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	$55.61	12.713%	$62.6797	$62.68	$62.70	$62.70
Purchase #2	$83.49	9.634%	$91.5334	$91.53	$91.55	$91.50
Purchase #3	$244.68	9.722%	$268.4678	$268.47	$268.45	$268.50
Purchase #4	$76.78	12.304%	$86.227	$86.23	$86.25	$86.20
Purchase #5	$51.95	5.456%	$54.7844	$54.78	$54.80	$54.80
Purchase #6	$64.42	12.739%	$72.6265	$72.63	$72.65	$72.60
Purchase #7	$50.81	9.161%	$55.4647	$55.46	$55.45	$55.50
7 purchase totals =	$627.74		$691.7835	$691.78	$691.85	$691.80