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 $148.27   3.113%   $152.8856   $152.89   $152.90   $152.90  
  Purchase #2 $194.51   12.618%   $219.0533   $219.05   $219.05   $219.10  
  Purchase #3 $61.76   4.741%   $64.688   $64.69   $64.70   $64.70  
  Purchase #4 $193.87   4.217%   $202.0455   $202.05   $202.05   $202.00  
  Purchase #5 $166.52   3.276%   $171.9752   $171.98   $172.00   $172.00  
  Purchase #6 $202.68   10.696%   $224.3587   $224.36   $224.35   $224.40  
  Purchase #7 $30.92   6.725%   $32.9994   $33.00   $33.00   $33.00  
  7 purchase totals = $998.53       $1,068.0057   $1,068.02   $1,068.05   $1,068.10