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	$60.92	11.221%	$67.7558	$67.76	$67.75	$67.80
Purchase #2	$116.39	6.244%	$123.6574	$123.66	$123.65	$123.70
Purchase #3	$34.95	8.268%	$37.8397	$37.84	$37.85	$37.80
Purchase #4	$186.59	7.342%	$200.2894	$200.29	$200.30	$200.30
Purchase #5	$148.76	12.743%	$167.7165	$167.72	$167.70	$167.70
Purchase #6	$46.55	6.110%	$49.3942	$49.39	$49.40	$49.40
Purchase #7	$137.27	6.567%	$146.2845	$146.28	$146.30	$146.30
7 purchase totals =	$731.43		$792.9375	$792.94	$792.95	$793.00