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	$59.28	3.178%	$61.1639	$61.16	$61.15	$61.20
Purchase #2	$233.35	10.378%	$257.5671	$257.57	$257.55	$257.60
Purchase #3	$37.27	13.289%	$42.2228	$42.22	$42.20	$42.20
Purchase #4	$156.97	4.539%	$164.0949	$164.09	$164.10	$164.10
Purchase #5	$57.51	11.405%	$64.069	$64.07	$64.05	$64.10
Purchase #6	$39.44	7.199%	$42.2793	$42.28	$42.30	$42.30
Purchase #7	$71.33	4.467%	$74.5163	$74.52	$74.50	$74.50
7 purchase totals =	$655.15		$705.9133	$705.91	$705.85	$706.00