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 $17.87   7.533%   $19.2161   $19.22   $19.20   $19.20  
  Purchase #2 $236.57   3.203%   $244.1473   $244.15   $244.15   $244.10  
  Purchase #3 $44.59   4.418%   $46.56   $46.56   $46.55   $46.60  
  Purchase #4 $221.87   5.679%   $234.47   $234.47   $234.45   $234.50  
  Purchase #5 $160.59   5.321%   $169.135   $169.14   $169.15   $169.10  
  Purchase #6 $161.58   8.375%   $175.1123   $175.11   $175.10   $175.10  
  Purchase #7 $152.61   12.309%   $171.3948   $171.39   $171.40   $171.40  
  7 purchase totals = $995.68       $1,060.0355   $1,060.04   $1,060.00   $1,060.00