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	$164.52	12.539%	$185.1492	$185.15	$185.15	$185.10
Purchase #2	$206.44	11.396%	$229.9659	$229.97	$229.95	$230.00
Purchase #3	$95.74	4.564%	$100.1096	$100.11	$100.10	$100.10
Purchase #4	$55.46	10.221%	$61.1286	$61.13	$61.15	$61.10
Purchase #5	$190.28	5.198%	$200.1708	$200.17	$200.15	$200.20
Purchase #6	$228.46	11.852%	$255.5371	$255.54	$255.55	$255.50
Purchase #7	$44.99	13.460%	$51.0457	$51.05	$51.05	$51.00
7 purchase totals =	$985.89		$1,083.1069	$1,083.12	$1,083.10	$1,083.00