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 $149.84   11.871%   $167.6275   $167.63   $167.65   $167.60  
  Purchase #2 $121.84   7.871%   $131.43   $131.43   $131.45   $131.40  
  Purchase #3 $103.68   6.296%   $110.2077   $110.21   $110.20   $110.20  
  Purchase #4 $230.99   4.436%   $241.2367   $241.24   $241.25   $241.20  
  Purchase #5 $158.70   11.754%   $177.3536   $177.35   $177.35   $177.40  
  Purchase #6 $212.89   4.111%   $221.6419   $221.64   $221.65   $221.60  
  Purchase #7 $113.95   8.645%   $123.801   $123.80   $123.80   $123.80  
  7 purchase totals = $1,091.89       $1,173.2984   $1,173.30   $1,173.35   $1,173.20