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	$89.74	13.634%	$101.9752	$101.98	$102.00	$102.00
Purchase #2	$10.29	11.715%	$11.4955	$11.50	$11.50	$11.50
Purchase #3	$206.53	6.321%	$219.5848	$219.58	$219.60	$219.60
Purchase #4	$173.45	7.171%	$185.8881	$185.89	$185.90	$185.90
Purchase #5	$245.41	11.358%	$273.2837	$273.28	$273.30	$273.30
Purchase #6	$101.27	11.741%	$113.1601	$113.16	$113.15	$113.20
Purchase #7	$149.83	10.307%	$165.273	$165.27	$165.25	$165.30
7 purchase totals =	$976.52		$1,070.6604	$1,070.66	$1,070.70	$1,070.80