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	$245.73	6.120%	$260.7687	$260.77	$260.75	$260.80
Purchase #2	$227.37	3.695%	$235.7713	$235.77	$235.75	$235.80
Purchase #3	$86.28	6.560%	$91.94	$91.94	$91.95	$91.90
Purchase #4	$54.81	3.264%	$56.599	$56.60	$56.60	$56.60
Purchase #5	$10.60	11.856%	$11.8567	$11.86	$11.85	$11.90
Purchase #6	$204.67	12.428%	$230.1064	$230.11	$230.10	$230.10
Purchase #7	$231.81	10.117%	$255.2622	$255.26	$255.25	$255.30
7 purchase totals =	$1,061.27		$1,142.3043	$1,142.31	$1,142.25	$1,142.40