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 $176.45   11.788%   $197.2499   $197.25   $197.25   $197.20  
  Purchase #2 $68.80   12.395%   $77.3278   $77.33   $77.35   $77.30  
  Purchase #3 $157.90   9.480%   $172.8689   $172.87   $172.85   $172.90  
  Purchase #4 $157.75   8.155%   $170.6145   $170.61   $170.60   $170.60  
  Purchase #5 $221.40   11.518%   $246.9009   $246.90   $246.90   $246.90  
  Purchase #6 $96.96   11.629%   $108.2355   $108.24   $108.25   $108.20  
  Purchase #7 $194.69   4.123%   $202.7171   $202.72   $202.70   $202.70  
  7 purchase totals = $1,073.95       $1,175.9146   $1,175.92   $1,175.90   $1,175.80