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	$148.39	9.580%	$162.6058	$162.61	$162.60	$162.60
Purchase #2	$28.93	10.561%	$31.9853	$31.99	$32.00	$32.00
Purchase #3	$244.74	9.336%	$267.5889	$267.59	$267.60	$267.60
Purchase #4	$43.26	4.181%	$45.0687	$45.07	$45.05	$45.10
Purchase #5	$113.27	3.569%	$117.3126	$117.31	$117.30	$117.30
Purchase #6	$142.58	7.371%	$153.0896	$153.09	$153.10	$153.10
Purchase #7	$214.78	4.814%	$225.1195	$225.12	$225.10	$225.10
7 purchase totals =	$935.95		$1,002.7704	$1,002.78	$1,002.75	$1,002.80