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 $158.76   10.202%   $174.9567   $174.96   $174.95   $175.00  
  Purchase #2 $235.75   12.613%   $265.4851   $265.49   $265.50   $265.50  
  Purchase #3 $227.37   5.707%   $240.346   $240.35   $240.35   $240.30  
  Purchase #4 $233.85   3.207%   $241.3496   $241.35   $241.35   $241.30  
  Purchase #5 $204.80   3.225%   $211.4048   $211.40   $211.40   $211.40  
  Purchase #6 $159.96   8.557%   $173.6478   $173.65   $173.65   $173.60  
  Purchase #7 $71.80   3.868%   $74.5772   $74.58   $74.60   $74.60  
  7 purchase totals = $1,292.29       $1,381.7672   $1,381.78   $1,381.80   $1,381.70