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 $244.52   6.573%   $260.5923   $260.59   $260.60   $260.60  
  Purchase #2 $163.57   6.742%   $174.5979   $174.60   $174.60   $174.60  
  Purchase #3 $206.40   10.590%   $228.2578   $228.26   $228.25   $228.30  
  Purchase #4 $62.59   4.242%   $65.2451   $65.25   $65.25   $65.20  
  Purchase #5 $207.79   3.441%   $214.9401   $214.94   $214.95   $214.90  
  Purchase #6 $43.84   13.489%   $49.7536   $49.75   $49.75   $49.80  
  Purchase #7 $145.89   5.102%   $153.3333   $153.33   $153.35   $153.30  
  7 purchase totals = $1,074.60       $1,146.7201   $1,146.72   $1,146.75   $1,146.70