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	$195.70	4.527%	$204.5593	$204.56	$204.55	$204.60
Purchase #2	$54.82	4.690%	$57.3911	$57.39	$57.40	$57.40
Purchase #3	$146.52	4.545%	$153.1793	$153.18	$153.20	$153.20
Purchase #4	$123.33	4.503%	$128.8835	$128.88	$128.90	$128.90
Purchase #5	$157.38	13.560%	$178.7207	$178.72	$178.70	$178.70
Purchase #6	$137.74	9.653%	$151.036	$151.04	$151.05	$151.00
Purchase #7	$172.75	13.636%	$196.3062	$196.31	$196.30	$196.30
7 purchase totals =	$988.24		$1,070.0761	$1,070.08	$1,070.10	$1,070.10