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	$215.41	3.315%	$222.5508	$222.55	$222.55	$222.60
Purchase #2	$21.86	10.515%	$24.1586	$24.16	$24.15	$24.20
Purchase #3	$145.59	4.851%	$152.6526	$152.65	$152.65	$152.70
Purchase #4	$146.49	13.554%	$166.3453	$166.35	$166.35	$166.30
Purchase #5	$89.59	10.621%	$99.1054	$99.11	$99.10	$99.10
Purchase #6	$44.59	12.153%	$50.009	$50.01	$50.00	$50.00
Purchase #7	$114.71	10.726%	$127.0138	$127.01	$127.00	$127.00
7 purchase totals =	$778.24		$841.8355	$841.84	$841.80	$841.90