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 $176.85   9.550%   $193.7392   $193.74   $193.75   $193.70  
  Purchase #2 $47.49   11.470%   $52.9371   $52.94   $52.95   $52.90  
  Purchase #3 $33.93   11.668%   $37.889   $37.89   $37.90   $37.90  
  Purchase #4 $240.40   7.169%   $257.6343   $257.63   $257.65   $257.60  
  Purchase #5 $56.35   5.142%   $59.2475   $59.25   $59.25   $59.20  
  Purchase #6 $218.29   4.584%   $228.2964   $228.30   $228.30   $228.30  
  Purchase #7 $65.42   10.342%   $72.1857   $72.19   $72.20   $72.20  
  7 purchase totals = $838.73       $901.9292   $901.94   $902.00   $901.80