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	$67.36	4.795%	$70.5899	$70.59	$70.60	$70.60
Purchase #2	$40.54	11.860%	$45.348	$45.35	$45.35	$45.30
Purchase #3	$76.86	13.522%	$87.253	$87.25	$87.25	$87.30
Purchase #4	$150.50	11.265%	$167.4538	$167.45	$167.45	$167.50
Purchase #5	$72.67	6.773%	$77.5919	$77.59	$77.60	$77.60
Purchase #6	$214.50	12.111%	$240.4781	$240.48	$240.50	$240.50
Purchase #7	$42.51	8.261%	$46.0218	$46.02	$46.00	$46.00
7 purchase totals =	$664.94		$734.7365	$734.73	$734.75	$734.80