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 $240.56   9.611%   $263.6802   $263.68   $263.70   $263.70  
  Purchase #2 $95.87   10.707%   $106.1348   $106.13   $106.15   $106.10  
  Purchase #3 $29.34   8.153%   $31.7321   $31.73   $31.75   $31.70  
  Purchase #4 $216.26   12.534%   $243.366   $243.37   $243.35   $243.40  
  Purchase #5 $237.60   9.736%   $260.7327   $260.73   $260.75   $260.70  
  Purchase #6 $108.86   5.436%   $114.7776   $114.78   $114.80   $114.80  
  Purchase #7 $67.51   10.466%   $74.5756   $74.58   $74.60   $74.60  
  7 purchase totals = $996.00       $1,094.9990   $1,095.00   $1,095.10   $1,095.00