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 $233.95   4.654%   $244.838   $244.84   $244.85   $244.80  
  Purchase #2 $117.58   6.421%   $125.1298   $125.13   $125.15   $125.10  
  Purchase #3 $21.62   11.182%   $24.0375   $24.04   $24.05   $24.00  
  Purchase #4 $157.52   12.281%   $176.865   $176.87   $176.85   $176.90  
  Purchase #5 $102.27   7.570%   $110.0118   $110.01   $110.00   $110.00  
  Purchase #6 $177.40   8.130%   $191.8226   $191.82   $191.80   $191.80  
  Purchase #7 $232.77   3.735%   $241.464   $241.46   $241.45   $241.50  
  7 purchase totals = $1,043.11       $1,114.1687   $1,114.17   $1,114.15   $1,114.10