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 $70.45   5.471%   $74.3043   $74.30   $74.30   $74.30  
  Purchase #2 $232.44   9.125%   $253.6502   $253.65   $253.65   $253.70  
  Purchase #3 $112.29   4.491%   $117.3329   $117.33   $117.35   $117.30  
  Purchase #4 $48.87   10.281%   $53.8943   $53.89   $53.90   $53.90  
  Purchase #5 $124.86   3.158%   $128.8031   $128.80   $128.80   $128.80  
  Purchase #6 $185.79   7.354%   $199.453   $199.45   $199.45   $199.50  
  Purchase #7 $219.74   7.447%   $236.104   $236.10   $236.10   $236.10  
  7 purchase totals = $994.44       $1,063.5418   $1,063.52   $1,063.55   $1,063.60