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 $160.78   8.336%   $174.1826   $174.18   $174.20   $174.20  
  Purchase #2 $226.66   4.363%   $236.5492   $236.55   $236.55   $236.50  
  Purchase #3 $9.97   5.533%   $10.5216   $10.52   $10.50   $10.50  
  Purchase #4 $98.93   9.119%   $107.9514   $107.95   $107.95   $108.00  
  Purchase #5 $107.39   4.154%   $111.851   $111.85   $111.85   $111.90  
  Purchase #6 $161.78   5.259%   $170.288   $170.29   $170.30   $170.30  
  Purchase #7 $246.85   10.665%   $273.1766   $273.18   $273.20   $273.20  
  7 purchase totals = $1,012.36       $1,084.5204   $1,084.52   $1,084.55   $1,084.60