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	$247.82	6.307%	$263.45	$263.45	$263.45	$263.50
Purchase #2	$41.32	12.364%	$46.4288	$46.43	$46.45	$46.40
Purchase #3	$145.97	8.198%	$157.9366	$157.94	$157.95	$157.90
Purchase #4	$180.55	4.192%	$188.1187	$188.12	$188.10	$188.10
Purchase #5	$141.66	9.763%	$155.4903	$155.49	$155.50	$155.50
Purchase #6	$42.87	4.313%	$44.719	$44.72	$44.70	$44.70
Purchase #7	$155.38	6.515%	$165.503	$165.50	$165.50	$165.50
7 purchase totals =	$955.57		$1,021.6464	$1,021.65	$1,021.65	$1,021.60