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	$96.47	9.840%	$105.9626	$105.96	$105.95	$106.00
Purchase #2	$36.80	3.274%	$38.0048	$38.00	$38.00	$38.00
Purchase #3	$145.78	4.653%	$152.5631	$152.56	$152.55	$152.60
Purchase #4	$48.97	11.170%	$54.4399	$54.44	$54.45	$54.40
Purchase #5	$104.76	13.195%	$118.5831	$118.58	$118.60	$118.60
Purchase #6	$45.97	10.359%	$50.732	$50.73	$50.75	$50.70
Purchase #7	$95.44	5.295%	$100.4935	$100.49	$100.50	$100.50
7 purchase totals =	$574.19		$620.7790	$620.76	$620.80	$620.80