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	$12.99	5.197%	$13.6651	$13.67	$13.65	$13.70
Purchase #2	$142.90	6.454%	$152.1228	$152.12	$152.10	$152.10
Purchase #3	$199.67	11.420%	$222.4723	$222.47	$222.45	$222.50
Purchase #4	$104.95	5.548%	$110.7726	$110.77	$110.75	$110.80
Purchase #5	$188.77	5.684%	$199.4997	$199.50	$199.50	$199.50
Purchase #6	$205.97	13.496%	$233.7677	$233.77	$233.75	$233.80
Purchase #7	$96.45	4.171%	$100.4729	$100.47	$100.45	$100.50
7 purchase totals =	$951.70		$1,032.7731	$1,032.77	$1,032.65	$1,032.90