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	$118.72	5.232%	$124.9314	$124.93	$124.95	$124.90
Purchase #2	$94.57	11.364%	$105.3169	$105.32	$105.30	$105.30
Purchase #3	$39.39	9.251%	$43.034	$43.03	$43.05	$43.00
Purchase #4	$141.45	8.769%	$153.8538	$153.85	$153.85	$153.90
Purchase #5	$181.32	11.353%	$201.9053	$201.91	$201.90	$201.90
Purchase #6	$81.95	10.748%	$90.758	$90.76	$90.75	$90.80
Purchase #7	$9.81	7.628%	$10.5583	$10.56	$10.55	$10.60
7 purchase totals =	$667.21		$730.3577	$730.36	$730.35	$730.40