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 $228.64   6.634%   $243.808   $243.81   $243.80   $243.80  
  Purchase #2 $31.29   6.165%   $33.219   $33.22   $33.20   $33.20  
  Purchase #3 $197.45   3.420%   $204.2028   $204.20   $204.20   $204.20  
  Purchase #4 $41.87   4.763%   $43.8643   $43.86   $43.85   $43.90  
  Purchase #5 $156.88   5.759%   $165.9147   $165.91   $165.90   $165.90  
  Purchase #6 $216.65   3.374%   $223.9598   $223.96   $223.95   $224.00  
  Purchase #7 $135.86   9.243%   $148.4175   $148.42   $148.40   $148.40  
  7 purchase totals = $1,008.64       $1,063.3861   $1,063.38   $1,063.30   $1,063.40