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	$77.78	6.782%	$83.055	$83.06	$83.05	$83.10
Purchase #2	$65.92	13.553%	$74.8541	$74.85	$74.85	$74.90
Purchase #3	$108.28	10.664%	$119.827	$119.83	$119.85	$119.80
Purchase #4	$117.64	10.781%	$130.3228	$130.32	$130.30	$130.30
Purchase #5	$213.38	4.773%	$223.5646	$223.56	$223.55	$223.60
Purchase #6	$215.64	4.110%	$224.5028	$224.50	$224.50	$224.50
Purchase #7	$173.46	4.316%	$180.9465	$180.95	$180.95	$180.90
7 purchase totals =	$972.10		$1,037.0728	$1,037.07	$1,037.05	$1,037.10