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 $58.32   4.700%   $61.061   $61.06   $61.05   $61.10  
  Purchase #2 $41.30   10.569%   $45.665   $45.67   $45.65   $45.70  
  Purchase #3 $232.83   11.222%   $258.9582   $258.96   $258.95   $259.00  
  Purchase #4 $45.70   5.313%   $48.128   $48.13   $48.15   $48.10  
  Purchase #5 $185.99   5.292%   $195.8326   $195.83   $195.85   $195.80  
  Purchase #6 $28.57   10.626%   $31.6058   $31.61   $31.60   $31.60  
  Purchase #7 $56.78   5.661%   $59.9943   $59.99   $60.00   $60.00  
  7 purchase totals = $649.49       $701.2449   $701.25   $701.25   $701.30