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 $112.36   4.220%   $117.1016   $117.10   $117.10   $117.10  
  Purchase #2 $206.55   13.700%   $234.8474   $234.85   $234.85   $234.80  
  Purchase #3 $42.45   12.107%   $47.5894   $47.59   $47.60   $47.60  
  Purchase #4 $169.28   10.438%   $186.9494   $186.95   $186.95   $186.90  
  Purchase #5 $95.95   11.270%   $106.7636   $106.76   $106.75   $106.80  
  Purchase #6 $167.98   7.227%   $180.1199   $180.12   $180.10   $180.10  
  Purchase #7 $206.99   8.858%   $225.3252   $225.33   $225.35   $225.30  
  7 purchase totals = $1,001.56       $1,098.6965   $1,098.70   $1,098.70   $1,098.60