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 $162.26   8.726%   $176.4188   $176.42   $176.40   $176.40  
  Purchase #2 $62.74   5.109%   $65.9454   $65.95   $65.95   $65.90  
  Purchase #3 $128.52   4.765%   $134.644   $134.64   $134.65   $134.60  
  Purchase #4 $58.61   9.742%   $64.3198   $64.32   $64.30   $64.30  
  Purchase #5 $167.36   10.653%   $185.1889   $185.19   $185.20   $185.20  
  Purchase #6 $29.81   12.198%   $33.4462   $33.45   $33.45   $33.40  
  Purchase #7 $89.30   5.442%   $94.1597   $94.16   $94.15   $94.20  
  7 purchase totals = $698.60       $754.1228   $754.13   $754.10   $754.00