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	$32.80	3.105%	$33.8184	$33.82	$33.80	$33.80
Purchase #2	$61.99	4.309%	$64.6611	$64.66	$64.65	$64.70
Purchase #3	$143.98	5.258%	$151.5505	$151.55	$151.55	$151.60
Purchase #4	$101.64	3.734%	$105.4352	$105.44	$105.45	$105.40
Purchase #5	$189.38	4.701%	$198.2828	$198.28	$198.30	$198.30
Purchase #6	$92.50	7.514%	$99.4505	$99.45	$99.45	$99.50
Purchase #7	$53.73	11.705%	$60.0191	$60.02	$60.00	$60.00
7 purchase totals =	$676.02		$713.2176	$713.22	$713.20	$713.30