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 $69.95   7.701%   $75.3368   $75.34   $75.35   $75.30  
  Purchase #2 $168.75   3.486%   $174.6326   $174.63   $174.65   $174.60  
  Purchase #3 $90.93   4.175%   $94.7263   $94.73   $94.75   $94.70  
  Purchase #4 $94.59   7.870%   $102.0342   $102.03   $102.05   $102.00  
  Purchase #5 $181.30   11.689%   $202.4922   $202.49   $202.50   $202.50  
  Purchase #6 $80.70   8.140%   $87.269   $87.27   $87.25   $87.30  
  Purchase #7 $10.86   5.456%   $11.4525   $11.45   $11.45   $11.50  
  7 purchase totals = $697.08       $747.9436   $747.94   $748.00   $747.90