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 $174.26   8.267%   $188.6661   $188.67   $188.65   $188.70  
  Purchase #2 $24.61   5.861%   $26.0524   $26.05   $26.05   $26.10  
  Purchase #3 $168.35   10.363%   $185.7961   $185.80   $185.80   $185.80  
  Purchase #4 $75.29   10.151%   $82.9327   $82.93   $82.95   $82.90  
  Purchase #5 $216.26   9.162%   $236.0737   $236.07   $236.05   $236.10  
  Purchase #6 $145.68   3.112%   $150.2136   $150.21   $150.20   $150.20  
  Purchase #7 $147.49   3.715%   $152.9693   $152.97   $152.95   $153.00  
  7 purchase totals = $951.94       $1,022.7039   $1,022.70   $1,022.65   $1,022.80