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	$77.81	6.452%	$82.8303	$82.83	$82.85	$82.80
Purchase #2	$8.83	3.567%	$9.145	$9.15	$9.15	$9.10
Purchase #3	$139.52	5.720%	$147.5005	$147.50	$147.50	$147.50
Purchase #4	$122.94	7.283%	$131.8937	$131.89	$131.90	$131.90
Purchase #5	$146.52	6.228%	$155.6453	$155.65	$155.65	$155.60
Purchase #6	$244.92	9.256%	$267.5898	$267.59	$267.60	$267.60
Purchase #7	$136.86	7.223%	$146.7454	$146.75	$146.75	$146.70
7 purchase totals =	$877.40		$941.3500	$941.36	$941.40	$941.20