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	$67.42	7.677%	$72.5958	$72.60	$72.60	$72.60
Purchase #2	$10.65	9.756%	$11.689	$11.69	$11.70	$11.70
Purchase #3	$100.28	6.174%	$106.4713	$106.47	$106.45	$106.50
Purchase #4	$6.74	10.806%	$7.4683	$7.47	$7.45	$7.50
Purchase #5	$86.85	5.659%	$91.7648	$91.76	$91.75	$91.80
Purchase #6	$133.82	4.277%	$139.5435	$139.54	$139.55	$139.50
Purchase #7	$55.79	6.791%	$59.5787	$59.58	$59.60	$59.60
7 purchase totals =	$461.55		$489.1114	$489.11	$489.10	$489.20