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 $62.49   10.717%   $69.1871   $69.19   $69.20   $69.20  
  Purchase #2 $157.80   4.152%   $164.3519   $164.35   $164.35   $164.40  
  Purchase #3 $68.98   6.339%   $73.3526   $73.35   $73.35   $73.40  
  Purchase #4 $89.51   6.222%   $95.0793   $95.08   $95.10   $95.10  
  Purchase #5 $246.84   8.595%   $268.0559   $268.06   $268.05   $268.10  
  Purchase #6 $88.54   7.694%   $95.3523   $95.35   $95.35   $95.40  
  Purchase #7 $202.54   5.707%   $214.099   $214.10   $214.10   $214.10  
  7 purchase totals = $916.70       $979.4781   $979.48   $979.50   $979.70