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	$225.89	4.188%	$235.3503	$235.35	$235.35	$235.40
Purchase #2	$144.73	13.408%	$164.1354	$164.14	$164.15	$164.10
Purchase #3	$30.62	6.272%	$32.5405	$32.54	$32.55	$32.50
Purchase #4	$113.38	6.379%	$120.6125	$120.61	$120.60	$120.60
Purchase #5	$108.83	5.142%	$114.426	$114.43	$114.45	$114.40
Purchase #6	$169.87	12.519%	$191.136	$191.14	$191.15	$191.10
Purchase #7	$131.45	11.241%	$146.2263	$146.23	$146.25	$146.20
7 purchase totals =	$924.77		$1,004.4270	$1,004.44	$1,004.50	$1,004.30