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 $67.59   11.838%   $75.5913   $75.59   $75.60   $75.60  
  Purchase #2 $139.41   8.653%   $151.4731   $151.47   $151.45   $151.50  
  Purchase #3 $123.94   6.736%   $132.2886   $132.29   $132.30   $132.30  
  Purchase #4 $139.65   5.499%   $147.3294   $147.33   $147.35   $147.30  
  Purchase #5 $73.45   5.613%   $77.5727   $77.57   $77.55   $77.60  
  Purchase #6 $100.43   3.776%   $104.2222   $104.22   $104.20   $104.20  
  Purchase #7 $85.72   9.751%   $94.0786   $94.08   $94.10   $94.10  
  7 purchase totals = $730.19       $782.5559   $782.55   $782.55   $782.60