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 $62.66   3.773%   $65.0242   $65.02   $65.00   $65.00  
  Purchase #2 $204.65   3.227%   $211.2541   $211.25   $211.25   $211.30  
  Purchase #3 $177.87   13.741%   $202.3111   $202.31   $202.30   $202.30  
  Purchase #4 $205.46   10.817%   $227.6846   $227.68   $227.70   $227.70  
  Purchase #5 $226.40   12.666%   $255.0758   $255.08   $255.10   $255.10  
  Purchase #6 $38.40   8.567%   $41.6897   $41.69   $41.70   $41.70  
  Purchase #7 $108.85   4.667%   $113.93   $113.93   $113.95   $113.90  
  7 purchase totals = $1,024.29       $1,116.9695   $1,116.96   $1,117.00   $1,117.00