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	$149.60	8.813%	$162.7842	$162.78	$162.80	$162.80
Purchase #2	$150.56	4.681%	$157.6077	$157.61	$157.60	$157.60
Purchase #3	$117.50	9.690%	$128.8858	$128.89	$128.90	$128.90
Purchase #4	$78.66	13.800%	$89.5151	$89.52	$89.50	$89.50
Purchase #5	$235.62	3.240%	$243.2541	$243.25	$243.25	$243.30
Purchase #6	$34.93	12.118%	$39.1628	$39.16	$39.15	$39.20
Purchase #7	$119.79	10.466%	$132.3272	$132.33	$132.35	$132.30
7 purchase totals =	$886.66		$953.5369	$953.54	$953.55	$953.60