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	$20.86	9.666%	$22.8763	$22.88	$22.90	$22.90
Purchase #2	$190.52	13.183%	$215.6363	$215.64	$215.65	$215.60
Purchase #3	$40.83	6.634%	$43.5387	$43.54	$43.55	$43.50
Purchase #4	$155.29	6.717%	$165.7208	$165.72	$165.70	$165.70
Purchase #5	$249.42	6.300%	$265.1335	$265.13	$265.15	$265.10
Purchase #6	$146.88	3.115%	$151.4553	$151.46	$151.45	$151.50
Purchase #7	$238.98	5.177%	$251.352	$251.35	$251.35	$251.40
7 purchase totals =	$1,042.78		$1,115.7129	$1,115.72	$1,115.75	$1,115.70