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 $83.75   13.766%   $95.279   $95.28   $95.30   $95.30  
  Purchase #2 $172.73   10.629%   $191.0895   $191.09   $191.10   $191.10  
  Purchase #3 $112.28   11.164%   $124.8149   $124.81   $124.80   $124.80  
  Purchase #4 $165.55   12.752%   $186.6609   $186.66   $186.65   $186.70  
  Purchase #5 $199.94   3.329%   $206.596   $206.60   $206.60   $206.60  
  Purchase #6 $88.99   11.376%   $99.1135   $99.11   $99.10   $99.10  
  Purchase #7 $197.81   3.377%   $204.49   $204.49   $204.50   $204.50  
  7 purchase totals = $1,021.05       $1,108.0438   $1,108.04   $1,108.05   $1,108.10