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 $67.76   3.319%   $70.009   $70.01   $70.00   $70.00  
  Purchase #2 $83.72   12.492%   $94.1783   $94.18   $94.20   $94.20  
  Purchase #3 $247.88   6.465%   $263.9054   $263.91   $263.90   $263.90  
  Purchase #4 $185.31   8.482%   $201.028   $201.03   $201.05   $201.00  
  Purchase #5 $179.54   5.364%   $189.1705   $189.17   $189.15   $189.20  
  Purchase #6 $100.49   11.807%   $112.3549   $112.35   $112.35   $112.40  
  Purchase #7 $110.85   5.722%   $117.1928   $117.19   $117.20   $117.20  
  7 purchase totals = $975.55       $1,047.8389   $1,047.84   $1,047.85   $1,047.90