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	$103.51	11.415%	$115.3257	$115.33	$115.35	$115.30
Purchase #2	$51.45	5.753%	$54.4099	$54.41	$54.40	$54.40
Purchase #3	$28.52	7.298%	$30.6014	$30.60	$30.60	$30.60
Purchase #4	$90.52	7.624%	$97.4212	$97.42	$97.40	$97.40
Purchase #5	$155.27	6.273%	$165.0101	$165.01	$165.00	$165.00
Purchase #6	$98.57	13.549%	$111.9252	$111.93	$111.95	$111.90
Purchase #7	$131.63	11.417%	$146.6582	$146.66	$146.65	$146.70
7 purchase totals =	$659.47		$721.3517	$721.36	$721.35	$721.30