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	$92.33	12.817%	$104.1639	$104.16	$104.15	$104.20
Purchase #2	$145.81	4.611%	$152.5333	$152.53	$152.55	$152.50
Purchase #3	$160.85	6.139%	$170.7246	$170.72	$170.70	$170.70
Purchase #4	$129.59	13.163%	$146.6479	$146.65	$146.65	$146.60
Purchase #5	$44.83	7.804%	$48.3285	$48.33	$48.35	$48.30
Purchase #6	$125.65	5.399%	$132.4338	$132.43	$132.45	$132.40
Purchase #7	$202.35	10.656%	$223.9124	$223.91	$223.90	$223.90
7 purchase totals =	$901.41		$978.7444	$978.73	$978.75	$978.60