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	$160.95	13.186%	$182.1729	$182.17	$182.15	$182.20
Purchase #2	$86.45	5.582%	$91.2756	$91.28	$91.30	$91.30
Purchase #3	$207.74	6.451%	$221.1413	$221.14	$221.15	$221.10
Purchase #4	$110.97	11.252%	$123.4563	$123.46	$123.45	$123.50
Purchase #5	$226.89	6.798%	$242.314	$242.31	$242.30	$242.30
Purchase #6	$111.78	13.531%	$126.905	$126.91	$126.90	$126.90
Purchase #7	$79.81	3.824%	$82.8619	$82.86	$82.85	$82.90
7 purchase totals =	$984.59		$1,070.1270	$1,070.13	$1,070.10	$1,070.20