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 $215.48   8.498%   $233.7915   $233.79   $233.80   $233.80  
  Purchase #2 $227.93   12.244%   $255.8377   $255.84   $255.85   $255.80  
  Purchase #3 $197.34   9.193%   $215.4815   $215.48   $215.50   $215.50  
  Purchase #4 $106.34   5.494%   $112.1823   $112.18   $112.20   $112.20  
  Purchase #5 $149.60   13.161%   $169.2889   $169.29   $169.30   $169.30  
  Purchase #6 $54.91   7.133%   $58.8267   $58.83   $58.85   $58.80  
  Purchase #7 $47.38   4.317%   $49.4254   $49.43   $49.45   $49.40  
  7 purchase totals = $998.98       $1,094.8340   $1,094.84   $1,094.95   $1,094.80