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 $180.42   7.525%   $193.9966   $194.00   $194.00   $194.00  
  Purchase #2 $239.38   11.389%   $266.643   $266.64   $266.65   $266.60  
  Purchase #3 $166.70   11.185%   $185.3454   $185.35   $185.35   $185.30  
  Purchase #4 $198.37   10.800%   $219.794   $219.79   $219.80   $219.80  
  Purchase #5 $47.37   10.288%   $52.2434   $52.24   $52.25   $52.20  
  Purchase #6 $41.52   9.363%   $45.4075   $45.41   $45.40   $45.40  
  Purchase #7 $128.53   9.800%   $141.1259   $141.13   $141.15   $141.10  
  7 purchase totals = $1,002.29       $1,104.5558   $1,104.56   $1,104.60   $1,104.40