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 $147.55   10.305%   $162.755   $162.76   $162.75   $162.80  
  Purchase #2 $233.45   4.846%   $244.763   $244.76   $244.75   $244.80  
  Purchase #3 $13.58   6.757%   $14.4976   $14.50   $14.50   $14.50  
  Purchase #4 $25.90   10.587%   $28.642   $28.64   $28.65   $28.60  
  Purchase #5 $156.49   9.231%   $170.9356   $170.94   $170.95   $170.90  
  Purchase #6 $169.59   3.701%   $175.8665   $175.87   $175.85   $175.90  
  Purchase #7 $246.59   6.481%   $262.5715   $262.57   $262.55   $262.60  
  7 purchase totals = $993.15       $1,060.0312   $1,060.04   $1,060.00   $1,060.10