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	$129.25	4.627%	$135.2304	$135.23	$135.25	$135.20
Purchase #2	$178.50	10.800%	$197.778	$197.78	$197.80	$197.80
Purchase #3	$111.26	4.626%	$116.4069	$116.41	$116.40	$116.40
Purchase #4	$202.81	5.344%	$213.6482	$213.65	$213.65	$213.60
Purchase #5	$51.51	11.527%	$57.4476	$57.45	$57.45	$57.40
Purchase #6	$204.39	12.420%	$229.7752	$229.78	$229.80	$229.80
Purchase #7	$99.74	11.401%	$111.1114	$111.11	$111.10	$111.10
7 purchase totals =	$977.46		$1,061.3977	$1,061.41	$1,061.45	$1,061.30