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	$65.76	11.412%	$73.2645	$73.26	$73.25	$73.30
Purchase #2	$152.72	6.282%	$162.3139	$162.31	$162.30	$162.30
Purchase #3	$19.62	11.646%	$21.9049	$21.90	$21.90	$21.90
Purchase #4	$242.33	7.504%	$260.5144	$260.51	$260.50	$260.50
Purchase #5	$34.62	7.865%	$37.3429	$37.34	$37.35	$37.30
Purchase #6	$107.30	11.652%	$119.8026	$119.80	$119.80	$119.80
Purchase #7	$175.97	13.859%	$200.3577	$200.36	$200.35	$200.40
7 purchase totals =	$798.32		$875.5009	$875.48	$875.45	$875.50