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 $60.36   5.496%   $63.6774   $63.68   $63.70   $63.70  
  Purchase #2 $236.38   6.156%   $250.9316   $250.93   $250.95   $250.90  
  Purchase #3 $204.52   7.145%   $219.133   $219.13   $219.15   $219.10  
  Purchase #4 $240.70   4.322%   $251.1031   $251.10   $251.10   $251.10  
  Purchase #5 $152.73   9.867%   $167.7999   $167.80   $167.80   $167.80  
  Purchase #6 $82.94   10.597%   $91.7292   $91.73   $91.75   $91.70  
  Purchase #7 $88.68   3.829%   $92.0756   $92.08   $92.10   $92.10  
  7 purchase totals = $1,066.31       $1,136.4498   $1,136.45   $1,136.55   $1,136.40