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	$57.66	8.531%	$62.579	$62.58	$62.60	$62.60
Purchase #2	$164.79	12.762%	$185.8205	$185.82	$185.80	$185.80
Purchase #3	$26.61	9.473%	$29.1308	$29.13	$29.15	$29.10
Purchase #4	$146.33	13.477%	$166.0509	$166.05	$166.05	$166.10
Purchase #5	$96.73	3.696%	$100.3051	$100.31	$100.30	$100.30
Purchase #6	$118.56	6.208%	$125.9202	$125.92	$125.90	$125.90
Purchase #7	$177.92	4.461%	$185.857	$185.86	$185.85	$185.90
7 purchase totals =	$788.60		$855.6635	$855.67	$855.65	$855.70