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	$238.45	8.422%	$258.5323	$258.53	$258.55	$258.50
Purchase #2	$114.78	7.375%	$123.245	$123.25	$123.25	$123.20
Purchase #3	$102.41	8.663%	$111.2818	$111.28	$111.30	$111.30
Purchase #4	$184.34	5.397%	$194.2888	$194.29	$194.30	$194.30
Purchase #5	$125.43	8.636%	$136.2621	$136.26	$136.25	$136.30
Purchase #6	$195.44	7.774%	$210.6335	$210.63	$210.65	$210.60
Purchase #7	$152.69	5.152%	$160.5566	$160.56	$160.55	$160.60
7 purchase totals =	$1,113.54		$1,194.8001	$1,194.80	$1,194.85	$1,194.80