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	$117.58	10.327%	$129.7225	$129.72	$129.70	$129.70
Purchase #2	$36.36	4.842%	$38.1206	$38.12	$38.10	$38.10
Purchase #3	$52.88	3.204%	$54.5743	$54.57	$54.55	$54.60
Purchase #4	$39.26	6.492%	$41.8088	$41.81	$41.80	$41.80
Purchase #5	$176.54	11.155%	$196.233	$196.23	$196.25	$196.20
Purchase #6	$91.96	13.592%	$104.4592	$104.46	$104.45	$104.50
Purchase #7	$159.66	3.609%	$165.4221	$165.42	$165.40	$165.40
7 purchase totals =	$674.24		$730.3405	$730.33	$730.25	$730.30