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 $65.52   5.423%   $69.0731   $69.07   $69.05   $69.10  
  Purchase #2 $243.80   3.746%   $252.9327   $252.93   $252.95   $252.90  
  Purchase #3 $161.53   4.441%   $168.7035   $168.70   $168.70   $168.70  
  Purchase #4 $140.54   7.399%   $150.9386   $150.94   $150.95   $150.90  
  Purchase #5 $32.44   3.167%   $33.4674   $33.47   $33.45   $33.50  
  Purchase #6 $120.52   9.110%   $131.4994   $131.50   $131.50   $131.50  
  Purchase #7 $193.78   5.220%   $203.8953   $203.90   $203.90   $203.90  
  7 purchase totals = $958.13       $1,010.5100   $1,010.51   $1,010.50   $1,010.50