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 $217.28   4.392%   $226.8229   $226.82   $226.80   $226.80  
  Purchase #2 $220.68   9.841%   $242.3971   $242.40   $242.40   $242.40  
  Purchase #3 $48.88   4.748%   $51.2008   $51.20   $51.20   $51.20  
  Purchase #4 $182.58   6.309%   $194.099   $194.10   $194.10   $194.10  
  Purchase #5 $62.58   9.595%   $68.5846   $68.58   $68.60   $68.60  
  Purchase #6 $178.66   13.835%   $203.3776   $203.38   $203.40   $203.40  
  Purchase #7 $57.53   12.144%   $64.5164   $64.52   $64.50   $64.50  
  7 purchase totals = $968.19       $1,050.9984   $1,051.00   $1,051.00   $1,051.00