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	$155.62	13.784%	$177.0707	$177.07	$177.05	$177.10
Purchase #2	$59.69	3.138%	$61.5631	$61.56	$61.55	$61.60
Purchase #3	$99.65	3.436%	$103.074	$103.07	$103.05	$103.10
Purchase #4	$103.60	7.345%	$111.2094	$111.21	$111.20	$111.20
Purchase #5	$57.78	4.623%	$60.4512	$60.45	$60.45	$60.50
Purchase #6	$44.52	3.192%	$45.9411	$45.94	$45.95	$45.90
Purchase #7	$50.29	10.676%	$55.659	$55.66	$55.65	$55.70
7 purchase totals =	$571.15		$614.9685	$614.96	$614.90	$615.10