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	$73.27	7.333%	$78.6429	$78.64	$78.65	$78.60
Purchase #2	$126.92	4.844%	$133.068	$133.07	$133.05	$133.10
Purchase #3	$192.35	8.817%	$209.3095	$209.31	$209.30	$209.30
Purchase #4	$134.42	9.545%	$147.2504	$147.25	$147.25	$147.30
Purchase #5	$178.96	9.624%	$196.1831	$196.18	$196.20	$196.20
Purchase #6	$131.28	6.567%	$139.9012	$139.90	$139.90	$139.90
Purchase #7	$141.62	12.286%	$159.0194	$159.02	$159.00	$159.00
7 purchase totals =	$978.82		$1,063.3745	$1,063.37	$1,063.35	$1,063.40