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 $57.77   7.279%   $61.9751   $61.98   $62.00   $62.00  
  Purchase #2 $115.74   9.548%   $126.7909   $126.79   $126.80   $126.80  
  Purchase #3 $182.71   8.559%   $198.3481   $198.35   $198.35   $198.30  
  Purchase #4 $247.84   10.266%   $273.2833   $273.28   $273.30   $273.30  
  Purchase #5 $88.79   6.453%   $94.5196   $94.52   $94.50   $94.50  
  Purchase #6 $192.29   4.296%   $200.5508   $200.55   $200.55   $200.60  
  Purchase #7 $81.35   10.185%   $89.6355   $89.64   $89.65   $89.60  
  7 purchase totals = $966.49       $1,045.1033   $1,045.11   $1,045.15   $1,045.10