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	$209.64	8.486%	$227.4301	$227.43	$227.45	$227.40
Purchase #2	$18.70	11.728%	$20.8931	$20.89	$20.90	$20.90
Purchase #3	$183.61	8.462%	$199.1471	$199.15	$199.15	$199.10
Purchase #4	$133.90	13.114%	$151.4596	$151.46	$151.45	$151.50
Purchase #5	$243.79	12.568%	$274.4295	$274.43	$274.45	$274.40
Purchase #6	$156.84	12.514%	$176.467	$176.47	$176.45	$176.50
Purchase #7	$190.49	8.326%	$206.3502	$206.35	$206.35	$206.40
7 purchase totals =	$1,136.97		$1,256.1766	$1,256.18	$1,256.20	$1,256.20