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	$176.57	13.707%	$200.7724	$200.77	$200.75	$200.80
Purchase #2	$114.99	7.425%	$123.528	$123.53	$123.55	$123.50
Purchase #3	$223.36	9.520%	$244.6239	$244.62	$244.60	$244.60
Purchase #4	$153.65	5.650%	$162.3312	$162.33	$162.35	$162.30
Purchase #5	$192.55	4.318%	$200.8643	$200.86	$200.85	$200.90
Purchase #6	$185.43	12.325%	$208.2842	$208.28	$208.30	$208.30
Purchase #7	$128.93	4.186%	$134.327	$134.33	$134.35	$134.30
7 purchase totals =	$1,175.48		$1,274.7310	$1,274.72	$1,274.75	$1,274.70