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 $186.74   5.498%   $197.007   $197.01   $197.00   $197.00  
  Purchase #2 $92.66   9.402%   $101.3719   $101.37   $101.35   $101.40  
  Purchase #3 $36.62   10.610%   $40.5054   $40.51   $40.50   $40.50  
  Purchase #4 $201.70   9.214%   $220.2846   $220.28   $220.30   $220.30  
  Purchase #5 $212.65   3.240%   $219.5399   $219.54   $219.55   $219.50  
  Purchase #6 $190.71   3.191%   $196.7956   $196.80   $196.80   $196.80  
  Purchase #7 $152.39   11.672%   $170.177   $170.18   $170.20   $170.20  
  7 purchase totals = $1,073.47       $1,145.6814   $1,145.69   $1,145.70   $1,145.70