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 $175.86   10.656%   $194.5996   $194.60   $194.60   $194.60  
  Purchase #2 $140.51   7.323%   $150.7995   $150.80   $150.80   $150.80  
  Purchase #3 $67.35   12.782%   $75.9587   $75.96   $75.95   $76.00  
  Purchase #4 $153.91   8.716%   $167.3248   $167.32   $167.30   $167.30  
  Purchase #5 $224.81   6.746%   $239.9757   $239.98   $240.00   $240.00  
  Purchase #6 $90.32   5.222%   $95.0365   $95.04   $95.05   $95.00  
  Purchase #7 $116.53   7.567%   $125.3478   $125.35   $125.35   $125.30  
  7 purchase totals = $969.29       $1,049.0426   $1,049.05   $1,049.05   $1,049.00