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 $128.53   10.112%   $141.527   $141.53   $141.55   $141.50  
  Purchase #2 $219.82   9.872%   $241.5206   $241.52   $241.50   $241.50  
  Purchase #3 $192.67   7.341%   $206.8139   $206.81   $206.80   $206.80  
  Purchase #4 $108.72   4.178%   $113.2623   $113.26   $113.25   $113.30  
  Purchase #5 $67.40   7.732%   $72.6114   $72.61   $72.60   $72.60  
  Purchase #6 $118.53   12.692%   $133.5738   $133.57   $133.55   $133.60  
  Purchase #7 $41.41   7.433%   $44.488   $44.49   $44.50   $44.50  
  7 purchase totals = $877.08       $953.7970   $953.79   $953.75   $953.80