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 $84.84   12.260%   $95.2414   $95.24   $95.25   $95.20  
  Purchase #2 $95.66   11.470%   $106.6322   $106.63   $106.65   $106.60  
  Purchase #3 $84.81   9.501%   $92.8678   $92.87   $92.85   $92.90  
  Purchase #4 $182.32   11.667%   $203.5913   $203.59   $203.60   $203.60  
  Purchase #5 $198.61   10.597%   $219.6567   $219.66   $219.65   $219.70  
  Purchase #6 $224.92   8.398%   $243.8088   $243.81   $243.80   $243.80  
  Purchase #7 $161.31   11.428%   $179.7445   $179.74   $179.75   $179.70  
  7 purchase totals = $1,032.47       $1,141.5427   $1,141.54   $1,141.55   $1,141.50