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	$179.42	9.145%	$195.828	$195.83	$195.85	$195.80
Purchase #2	$51.69	6.197%	$54.8932	$54.89	$54.90	$54.90
Purchase #3	$179.73	9.233%	$196.3245	$196.32	$196.30	$196.30
Purchase #4	$233.42	7.363%	$250.6067	$250.61	$250.60	$250.60
Purchase #5	$130.76	12.507%	$147.1142	$147.11	$147.10	$147.10
Purchase #6	$47.65	11.727%	$53.2379	$53.24	$53.25	$53.20
Purchase #7	$11.97	6.224%	$12.715	$12.72	$12.70	$12.70
7 purchase totals =	$834.64		$910.7195	$910.72	$910.70	$910.60