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 $61.43   13.385%   $69.6524   $69.65   $69.65   $69.70  
  Purchase #2 $165.98   4.807%   $173.9587   $173.96   $173.95   $174.00  
  Purchase #3 $95.51   12.353%   $107.3084   $107.31   $107.30   $107.30  
  Purchase #4 $181.32   12.113%   $203.2833   $203.28   $203.30   $203.30  
  Purchase #5 $215.63   7.754%   $232.35   $232.35   $232.35   $232.40  
  Purchase #6 $235.79   3.706%   $244.5284   $244.53   $244.55   $244.50  
  Purchase #7 $123.92   12.129%   $138.9503   $138.95   $138.95   $139.00  
  7 purchase totals = $1,079.58       $1,170.0315   $1,170.03   $1,170.05   $1,170.20