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 $121.73   3.502%   $125.993   $125.99   $126.00   $126.00  
  Purchase #2 $203.51   5.332%   $214.3612   $214.36   $214.35   $214.40  
  Purchase #3 $223.46   5.818%   $236.4609   $236.46   $236.45   $236.50  
  Purchase #4 $11.62   5.766%   $12.29   $12.29   $12.30   $12.30  
  Purchase #5 $165.35   7.391%   $177.571   $177.57   $177.55   $177.60  
  Purchase #6 $59.71   7.508%   $64.193   $64.19   $64.20   $64.20  
  Purchase #7 $223.98   9.368%   $244.9624   $244.96   $244.95   $245.00  
  7 purchase totals = $1,009.36       $1,075.8315   $1,075.82   $1,075.80   $1,076.00