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	$191.60	4.768%	$200.7355	$200.74	$200.75	$200.70
Purchase #2	$211.52	8.473%	$229.4421	$229.44	$229.45	$229.40
Purchase #3	$220.63	12.511%	$248.233	$248.23	$248.25	$248.20
Purchase #4	$16.28	13.729%	$18.5151	$18.52	$18.50	$18.50
Purchase #5	$52.92	12.782%	$59.6842	$59.68	$59.70	$59.70
Purchase #6	$146.99	4.176%	$153.1283	$153.13	$153.15	$153.10
Purchase #7	$160.38	6.533%	$170.8576	$170.86	$170.85	$170.90
7 purchase totals =	$1,000.32		$1,080.5958	$1,080.60	$1,080.65	$1,080.50