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	$190.80	8.206%	$206.457	$206.46	$206.45	$206.50
Purchase #2	$50.65	11.369%	$56.4084	$56.41	$56.40	$56.40
Purchase #3	$87.51	13.607%	$99.4175	$99.42	$99.40	$99.40
Purchase #4	$85.72	5.447%	$90.3892	$90.39	$90.40	$90.40
Purchase #5	$214.76	3.766%	$222.8479	$222.85	$222.85	$222.80
Purchase #6	$103.61	10.363%	$114.3471	$114.35	$114.35	$114.30
Purchase #7	$54.35	13.414%	$61.6405	$61.64	$61.65	$61.60
7 purchase totals =	$787.40		$851.5076	$851.52	$851.50	$851.40