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	$134.66	11.194%	$149.7338	$149.73	$149.75	$149.70
Purchase #2	$123.89	11.606%	$138.2687	$138.27	$138.25	$138.30
Purchase #3	$181.57	5.211%	$191.0316	$191.03	$191.05	$191.00
Purchase #4	$158.78	7.621%	$170.8806	$170.88	$170.90	$170.90
Purchase #5	$124.81	13.224%	$141.3149	$141.31	$141.30	$141.30
Purchase #6	$54.25	9.656%	$59.4884	$59.49	$59.50	$59.50
Purchase #7	$132.47	3.519%	$137.1316	$137.13	$137.15	$137.10
7 purchase totals =	$910.43		$987.8496	$987.84	$987.90	$987.80