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	$50.85	4.808%	$53.2949	$53.29	$53.30	$53.30
Purchase #2	$19.57	5.168%	$20.5814	$20.58	$20.60	$20.60
Purchase #3	$79.33	4.777%	$83.1196	$83.12	$83.10	$83.10
Purchase #4	$176.67	5.252%	$185.9487	$185.95	$185.95	$185.90
Purchase #5	$136.92	4.205%	$142.6775	$142.68	$142.70	$142.70
Purchase #6	$153.41	7.450%	$164.839	$164.84	$164.85	$164.80
Purchase #7	$144.32	3.345%	$149.1475	$149.15	$149.15	$149.10
7 purchase totals =	$761.07		$799.6086	$799.61	$799.65	$799.50