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 $44.70   3.168%   $46.1161   $46.12   $46.10   $46.10  
  Purchase #2 $174.57   10.745%   $193.3275   $193.33   $193.35   $193.30  
  Purchase #3 $10.25   5.386%   $10.8021   $10.80   $10.80   $10.80  
  Purchase #4 $198.92   5.601%   $210.0615   $210.06   $210.05   $210.10  
  Purchase #5 $220.79   3.267%   $228.0032   $228.00   $228.00   $228.00  
  Purchase #6 $244.30   6.769%   $260.8367   $260.84   $260.85   $260.80  
  Purchase #7 $63.82   7.417%   $68.5535   $68.55   $68.55   $68.60  
  7 purchase totals = $957.35       $1,017.7006   $1,017.70   $1,017.70   $1,017.70