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 $85.59   8.228%   $92.6323   $92.63   $92.65   $92.60  
  Purchase #2 $169.85   6.782%   $181.3692   $181.37   $181.35   $181.40  
  Purchase #3 $149.92   13.142%   $169.6225   $169.62   $169.60   $169.60  
  Purchase #4 $181.97   11.714%   $203.286   $203.29   $203.30   $203.30  
  Purchase #5 $115.40   12.102%   $129.3657   $129.37   $129.35   $129.40  
  Purchase #6 $186.58   9.600%   $204.4917   $204.49   $204.50   $204.50  
  Purchase #7 $65.31   11.552%   $72.8546   $72.85   $72.85   $72.90  
  7 purchase totals = $954.62       $1,053.6220   $1,053.62   $1,053.60   $1,053.70