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	$139.72	4.479%	$145.9781	$145.98	$146.00	$146.00
Purchase #2	$213.62	5.535%	$225.4439	$225.44	$225.45	$225.40
Purchase #3	$151.54	10.281%	$167.1198	$167.12	$167.10	$167.10
Purchase #4	$85.38	8.743%	$92.8448	$92.84	$92.85	$92.80
Purchase #5	$127.62	8.118%	$137.9802	$137.98	$138.00	$138.00
Purchase #6	$59.81	11.470%	$66.6702	$66.67	$66.65	$66.70
Purchase #7	$248.59	6.114%	$263.7888	$263.79	$263.80	$263.80
7 purchase totals =	$1,026.28		$1,099.8258	$1,099.82	$1,099.85	$1,099.80