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 $176.65   13.774%   $200.9818   $200.98   $201.00   $201.00  
  Purchase #2 $244.55   7.758%   $263.5222   $263.52   $263.50   $263.50  
  Purchase #3 $25.43   10.747%   $28.163   $28.16   $28.15   $28.20  
  Purchase #4 $189.26   11.292%   $210.6312   $210.63   $210.65   $210.60  
  Purchase #5 $72.75   12.816%   $82.0736   $82.07   $82.05   $82.10  
  Purchase #6 $194.68   7.293%   $208.878   $208.88   $208.90   $208.90  
  Purchase #7 $147.78   7.321%   $158.599   $158.60   $158.60   $158.60  
  7 purchase totals = $1,051.10       $1,152.8488   $1,152.84   $1,152.85   $1,152.90