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	$34.92	4.726%	$36.5703	$36.57	$36.55	$36.60
Purchase #2	$103.47	12.410%	$116.3106	$116.31	$116.30	$116.30
Purchase #3	$57.34	10.843%	$63.5574	$63.56	$63.55	$63.60
Purchase #4	$17.52	12.810%	$19.7643	$19.76	$19.75	$19.80
Purchase #5	$86.57	13.612%	$98.3539	$98.35	$98.35	$98.40
Purchase #6	$18.29	10.817%	$20.2684	$20.27	$20.25	$20.30
Purchase #7	$77.95	5.865%	$82.5218	$82.52	$82.50	$82.50
7 purchase totals =	$396.06		$437.3467	$437.34	$437.25	$437.50