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	$54.55	12.117%	$61.1598	$61.16	$61.15	$61.20
Purchase #2	$117.95	4.737%	$123.5373	$123.54	$123.55	$123.50
Purchase #3	$145.46	6.128%	$154.3738	$154.37	$154.35	$154.40
Purchase #4	$206.85	13.245%	$234.2473	$234.25	$234.25	$234.20
Purchase #5	$152.49	10.684%	$168.782	$168.78	$168.80	$168.80
Purchase #6	$213.90	11.475%	$238.445	$238.45	$238.45	$238.40
Purchase #7	$34.30	8.399%	$37.1809	$37.18	$37.20	$37.20
7 purchase totals =	$925.50		$1,017.7261	$1,017.73	$1,017.75	$1,017.70