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 $218.66   8.529%   $237.3095   $237.31   $237.30   $237.30  
  Purchase #2 $223.87   6.253%   $237.8686   $237.87   $237.85   $237.90  
  Purchase #3 $58.34   11.740%   $65.1891   $65.19   $65.20   $65.20  
  Purchase #4 $47.29   5.209%   $49.7533   $49.75   $49.75   $49.80  
  Purchase #5 $188.65   11.568%   $210.473   $210.47   $210.45   $210.50  
  Purchase #6 $240.93   13.791%   $274.1567   $274.16   $274.15   $274.20  
  Purchase #7 $55.25   7.443%   $59.3623   $59.36   $59.35   $59.40  
  7 purchase totals = $1,032.99       $1,134.1125   $1,134.11   $1,134.05   $1,134.30