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 $51.69   7.832%   $55.7384   $55.74   $55.75   $55.70  
  Purchase #2 $119.53   7.378%   $128.3489   $128.35   $128.35   $128.30  
  Purchase #3 $207.74   5.608%   $219.3901   $219.39   $219.40   $219.40  
  Purchase #4 $186.66   4.355%   $194.789   $194.79   $194.80   $194.80  
  Purchase #5 $183.29   4.428%   $191.4061   $191.41   $191.40   $191.40  
  Purchase #6 $240.30   5.873%   $254.4128   $254.41   $254.40   $254.40  
  Purchase #7 $23.37   6.754%   $24.9484   $24.95   $24.95   $24.90  
  7 purchase totals = $1,012.58       $1,069.0337   $1,069.04   $1,069.05   $1,068.90