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	$48.45	7.841%	$52.249	$52.25	$52.25	$52.20
Purchase #2	$144.82	13.774%	$164.7675	$164.77	$164.75	$164.80
Purchase #3	$150.52	9.646%	$165.0392	$165.04	$165.05	$165.00
Purchase #4	$200.54	5.135%	$210.8377	$210.84	$210.85	$210.80
Purchase #5	$241.31	3.232%	$249.1091	$249.11	$249.10	$249.10
Purchase #6	$153.38	3.749%	$159.1302	$159.13	$159.15	$159.10
Purchase #7	$9.52	9.136%	$10.3897	$10.39	$10.40	$10.40
7 purchase totals =	$948.54		$1,011.5224	$1,011.53	$1,011.55	$1,011.40