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 $59.68   7.154%   $63.9495   $63.95   $63.95   $63.90  
  Purchase #2 $91.86   6.197%   $97.5526   $97.55   $97.55   $97.60  
  Purchase #3 $153.44   4.567%   $160.4476   $160.45   $160.45   $160.40  
  Purchase #4 $212.97   11.732%   $237.9556   $237.96   $237.95   $238.00  
  Purchase #5 $211.90   8.813%   $230.5747   $230.57   $230.55   $230.60  
  Purchase #6 $110.45   4.578%   $115.5064   $115.51   $115.50   $115.50  
  Purchase #7 $211.65   4.328%   $220.8102   $220.81   $220.80   $220.80  
  7 purchase totals = $1,051.95       $1,126.7966   $1,126.80   $1,126.75   $1,126.80