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	$204.65	8.122%	$221.2717	$221.27	$221.25	$221.30
Purchase #2	$111.58	4.517%	$116.6201	$116.62	$116.60	$116.60
Purchase #3	$31.49	4.570%	$32.9291	$32.93	$32.95	$32.90
Purchase #4	$114.33	10.423%	$126.2466	$126.25	$126.25	$126.20
Purchase #5	$110.45	8.771%	$120.1376	$120.14	$120.15	$120.10
Purchase #6	$158.43	9.146%	$172.92	$172.92	$172.90	$172.90
Purchase #7	$22.76	13.736%	$25.8863	$25.89	$25.90	$25.90
7 purchase totals =	$753.69		$816.0114	$816.02	$816.00	$815.90