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	$144.61	5.501%	$152.565	$152.57	$152.55	$152.60
Purchase #2	$212.48	11.300%	$236.4902	$236.49	$236.50	$236.50
Purchase #3	$41.73	8.387%	$45.2299	$45.23	$45.25	$45.20
Purchase #4	$16.63	8.436%	$18.0329	$18.03	$18.05	$18.00
Purchase #5	$165.28	12.462%	$185.8772	$185.88	$185.90	$185.90
Purchase #6	$36.66	5.704%	$38.7511	$38.75	$38.75	$38.80
Purchase #7	$153.27	3.469%	$158.5869	$158.59	$158.60	$158.60
7 purchase totals =	$770.66		$835.5332	$835.54	$835.60	$835.60