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	$72.56	3.390%	$75.0198	$75.02	$75.00	$75.00
Purchase #2	$137.83	12.517%	$155.0822	$155.08	$155.10	$155.10
Purchase #3	$53.64	4.589%	$56.1015	$56.10	$56.10	$56.10
Purchase #4	$120.89	5.597%	$127.6562	$127.66	$127.65	$127.70
Purchase #5	$235.97	7.598%	$253.899	$253.90	$253.90	$253.90
Purchase #6	$188.56	6.433%	$200.6901	$200.69	$200.70	$200.70
Purchase #7	$214.47	7.178%	$229.8647	$229.86	$229.85	$229.90
7 purchase totals =	$1,023.92		$1,098.3135	$1,098.31	$1,098.30	$1,098.40