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	$109.67	12.474%	$123.3502	$123.35	$123.35	$123.40
Purchase #2	$95.77	4.810%	$100.3765	$100.38	$100.40	$100.40
Purchase #3	$70.43	8.716%	$76.5687	$76.57	$76.55	$76.60
Purchase #4	$222.93	9.323%	$243.7138	$243.71	$243.70	$243.70
Purchase #5	$230.71	4.572%	$241.2581	$241.26	$241.25	$241.30
Purchase #6	$156.92	9.798%	$172.295	$172.30	$172.30	$172.30
Purchase #7	$69.50	12.516%	$78.1986	$78.20	$78.20	$78.20
7 purchase totals =	$955.93		$1,035.7609	$1,035.77	$1,035.75	$1,035.90