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 $212.65   6.631%   $226.7508   $226.75   $226.75   $226.80  
  Purchase #2 $208.78   8.582%   $226.6975   $226.70   $226.70   $226.70  
  Purchase #3 $172.82   5.426%   $182.1972   $182.20   $182.20   $182.20  
  Purchase #4 $53.94   9.608%   $59.1226   $59.12   $59.10   $59.10  
  Purchase #5 $137.64   8.674%   $149.5789   $149.58   $149.60   $149.60  
  Purchase #6 $62.71   4.413%   $65.4774   $65.48   $65.50   $65.50  
  Purchase #7 $136.66   11.478%   $152.3458   $152.35   $152.35   $152.30  
  7 purchase totals = $985.20       $1,062.1702   $1,062.18   $1,062.20   $1,062.20