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 $198.52   6.410%   $211.2451   $211.25   $211.25   $211.20  
  Purchase #2 $225.57   9.692%   $247.4322   $247.43   $247.45   $247.40  
  Purchase #3 $46.82   6.539%   $49.8816   $49.88   $49.90   $49.90  
  Purchase #4 $100.76   12.410%   $113.2643   $113.26   $113.25   $113.30  
  Purchase #5 $78.46   9.513%   $85.9239   $85.92   $85.90   $85.90  
  Purchase #6 $153.49   11.279%   $170.8021   $170.80   $170.80   $170.80  
  Purchase #7 $182.55   8.594%   $198.2383   $198.24   $198.25   $198.20  
  7 purchase totals = $986.17       $1,076.7875   $1,076.78   $1,076.80   $1,076.70