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	$33.66	7.160%	$36.0701	$36.07	$36.05	$36.10
Purchase #2	$154.50	8.589%	$167.77	$167.77	$167.75	$167.80
Purchase #3	$223.28	10.627%	$247.008	$247.01	$247.00	$247.00
Purchase #4	$137.92	10.490%	$152.3878	$152.39	$152.40	$152.40
Purchase #5	$33.41	12.762%	$37.6738	$37.67	$37.65	$37.70
Purchase #6	$173.94	10.346%	$191.9358	$191.94	$191.95	$191.90
Purchase #7	$175.29	9.451%	$191.8567	$191.86	$191.85	$191.90
7 purchase totals =	$932.00		$1,024.7022	$1,024.71	$1,024.65	$1,024.80