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	$148.41	5.866%	$157.1157	$157.12	$157.10	$157.10
Purchase #2	$147.41	13.774%	$167.7143	$167.71	$167.70	$167.70
Purchase #3	$197.77	12.328%	$222.1511	$222.15	$222.15	$222.20
Purchase #4	$152.59	4.419%	$159.333	$159.33	$159.35	$159.30
Purchase #5	$204.55	8.667%	$222.2783	$222.28	$222.30	$222.30
Purchase #6	$126.51	3.541%	$130.9897	$130.99	$131.00	$131.00
Purchase #7	$167.84	13.616%	$190.6931	$190.69	$190.70	$190.70
7 purchase totals =	$1,145.08		$1,250.2752	$1,250.27	$1,250.30	$1,250.30