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 $88.72   7.103%   $95.0218   $95.02   $95.00   $95.00  
  Purchase #2 $230.89   6.557%   $246.0295   $246.03   $246.05   $246.00  
  Purchase #3 $55.59   8.128%   $60.1084   $60.11   $60.10   $60.10  
  Purchase #4 $183.76   4.198%   $191.4742   $191.47   $191.45   $191.50  
  Purchase #5 $10.43   10.708%   $11.5468   $11.55   $11.55   $11.50  
  Purchase #6 $119.28   7.363%   $128.0626   $128.06   $128.05   $128.10  
  Purchase #7 $130.27   9.592%   $142.7655   $142.77   $142.75   $142.80  
  7 purchase totals = $818.94       $875.0088   $875.01   $874.95   $875.00