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	$67.57	11.764%	$75.5189	$75.52	$75.50	$75.50
Purchase #2	$163.28	13.190%	$184.8166	$184.82	$184.80	$184.80
Purchase #3	$73.69	12.840%	$83.1518	$83.15	$83.15	$83.20
Purchase #4	$211.65	13.347%	$239.8989	$239.90	$239.90	$239.90
Purchase #5	$123.62	4.568%	$129.267	$129.27	$129.25	$129.30
Purchase #6	$111.28	4.470%	$116.2542	$116.25	$116.25	$116.30
Purchase #7	$145.43	5.140%	$152.9051	$152.91	$152.90	$152.90
7 purchase totals =	$896.52		$981.8125	$981.82	$981.75	$981.90