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	$111.84	8.146%	$120.9505	$120.95	$120.95	$121.00
Purchase #2	$173.92	11.813%	$194.4652	$194.47	$194.45	$194.50
Purchase #3	$172.27	13.480%	$195.492	$195.49	$195.50	$195.50
Purchase #4	$41.89	5.821%	$44.3284	$44.33	$44.35	$44.30
Purchase #5	$121.47	4.818%	$127.3224	$127.32	$127.30	$127.30
Purchase #6	$147.25	7.562%	$158.385	$158.39	$158.40	$158.40
Purchase #7	$182.89	5.264%	$192.5173	$192.52	$192.50	$192.50
7 purchase totals =	$951.53		$1,033.4608	$1,033.47	$1,033.45	$1,033.50