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	$187.33	7.249%	$200.9096	$200.91	$200.90	$200.90
Purchase #2	$19.85	7.367%	$21.3123	$21.31	$21.30	$21.30
Purchase #3	$91.58	4.428%	$95.6352	$95.64	$95.65	$95.60
Purchase #4	$191.65	4.691%	$200.6403	$200.64	$200.65	$200.60
Purchase #5	$10.49	3.529%	$10.8602	$10.86	$10.85	$10.90
Purchase #6	$18.97	5.564%	$20.0255	$20.03	$20.05	$20.00
Purchase #7	$127.61	8.545%	$138.5143	$138.51	$138.50	$138.50
7 purchase totals =	$647.48		$687.8974	$687.90	$687.90	$687.80