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 $213.93   5.451%   $225.5913   $225.59   $225.60   $225.60  
  Purchase #2 $110.52   11.339%   $123.0519   $123.05   $123.05   $123.10  
  Purchase #3 $169.69   12.576%   $191.0302   $191.03   $191.05   $191.00  
  Purchase #4 $107.36   12.819%   $121.1225   $121.12   $121.10   $121.10  
  Purchase #5 $237.96   5.596%   $251.2762   $251.28   $251.30   $251.30  
  Purchase #6 $101.55   8.287%   $109.9654   $109.97   $109.95   $110.00  
  Purchase #7 $28.47   8.821%   $30.9813   $30.98   $31.00   $31.00  
  7 purchase totals = $969.48       $1,053.0188   $1,053.02   $1,053.05   $1,053.10