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	$145.87	8.556%	$158.3506	$158.35	$158.35	$158.40
Purchase #2	$175.87	8.215%	$190.3177	$190.32	$190.30	$190.30
Purchase #3	$80.71	11.401%	$89.9117	$89.91	$89.90	$89.90
Purchase #4	$59.62	10.717%	$66.0095	$66.01	$66.00	$66.00
Purchase #5	$211.54	12.380%	$237.7287	$237.73	$237.75	$237.70
Purchase #6	$60.61	11.421%	$67.5323	$67.53	$67.55	$67.50
Purchase #7	$147.69	3.627%	$153.0467	$153.05	$153.05	$153.00
7 purchase totals =	$881.91		$962.8972	$962.90	$962.90	$962.80