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 $93.87   8.270%   $101.633   $101.63   $101.65   $101.60  
  Purchase #2 $232.76   9.325%   $254.4649   $254.46   $254.45   $254.50  
  Purchase #3 $246.68   7.287%   $264.6556   $264.66   $264.65   $264.70  
  Purchase #4 $149.69   10.454%   $165.3386   $165.34   $165.35   $165.30  
  Purchase #5 $237.69   13.580%   $269.9683   $269.97   $269.95   $270.00  
  Purchase #6 $243.77   6.389%   $259.3445   $259.34   $259.35   $259.30  
  Purchase #7 $45.45   6.851%   $48.5638   $48.56   $48.55   $48.60  
  7 purchase totals = $1,249.91       $1,363.9687   $1,363.96   $1,363.95   $1,364.00