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	$182.69	12.308%	$205.1755	$205.18	$205.20	$205.20
Purchase #2	$142.71	12.298%	$160.2605	$160.26	$160.25	$160.30
Purchase #3	$106.99	10.544%	$118.271	$118.27	$118.25	$118.30
Purchase #4	$100.73	4.553%	$105.3162	$105.32	$105.30	$105.30
Purchase #5	$130.56	5.111%	$137.2329	$137.23	$137.25	$137.20
Purchase #6	$48.53	10.382%	$53.5684	$53.57	$53.55	$53.60
Purchase #7	$247.64	6.329%	$263.3131	$263.31	$263.30	$263.30
7 purchase totals =	$959.85		$1,043.1376	$1,043.14	$1,043.10	$1,043.20