Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $213.71   9.849%   $234.7583   $234.76   $234.75   $234.80  
  Purchase #2 $181.67   7.253%   $194.8465   $194.85   $194.85   $194.80  
  Purchase #3 $242.94   12.279%   $272.7706   $272.77   $272.75   $272.80  
  Purchase #4 $219.89   6.835%   $234.9195   $234.92   $234.90   $234.90  
  Purchase #5 $184.37   10.428%   $203.5961   $203.60   $203.60   $203.60  
  Purchase #6 $207.49   7.244%   $222.5206   $222.52   $222.50   $222.50  
  Purchase #7 $98.94   7.214%   $106.0775   $106.08   $106.10   $106.10  
  7 purchase totals = $1,349.01       $1,469.4891   $1,469.50   $1,469.45   $1,469.50