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	$126.72	6.430%	$134.8681	$134.87	$134.85	$134.90
Purchase #2	$139.43	8.673%	$151.5228	$151.52	$151.50	$151.50
Purchase #3	$139.60	11.683%	$155.9095	$155.91	$155.90	$155.90
Purchase #4	$144.75	5.183%	$152.2524	$152.25	$152.25	$152.30
Purchase #5	$223.94	5.223%	$235.6364	$235.64	$235.65	$235.60
Purchase #6	$143.65	4.705%	$150.4087	$150.41	$150.40	$150.40
Purchase #7	$56.96	13.814%	$64.8285	$64.83	$64.85	$64.80
7 purchase totals =	$975.05		$1,045.4264	$1,045.43	$1,045.40	$1,045.40