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 $193.61   5.444%   $204.1501   $204.15   $204.15   $204.20  
  Purchase #2 $24.88   8.327%   $26.9518   $26.95   $26.95   $27.00  
  Purchase #3 $82.65   11.307%   $91.9952   $92.00   $92.00   $92.00  
  Purchase #4 $67.90   3.253%   $70.1088   $70.11   $70.10   $70.10  
  Purchase #5 $60.84   5.408%   $64.1302   $64.13   $64.15   $64.10  
  Purchase #6 $109.49   8.409%   $118.697   $118.70   $118.70   $118.70  
  Purchase #7 $201.32   4.707%   $210.7961   $210.80   $210.80   $210.80  
  7 purchase totals = $740.69       $786.8292   $786.84   $786.85   $786.90