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	$54.44	12.172%	$61.0664	$61.07	$61.05	$61.10
Purchase #2	$100.95	4.795%	$105.7906	$105.79	$105.80	$105.80
Purchase #3	$81.45	5.286%	$85.7554	$85.76	$85.75	$85.80
Purchase #4	$186.42	7.163%	$199.7733	$199.77	$199.75	$199.80
Purchase #5	$167.89	12.522%	$188.9132	$188.91	$188.90	$188.90
Purchase #6	$159.46	10.359%	$175.9785	$175.98	$176.00	$176.00
Purchase #7	$240.93	11.349%	$268.2731	$268.27	$268.25	$268.30
7 purchase totals =	$991.54		$1,085.5505	$1,085.55	$1,085.50	$1,085.70