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	$224.94	7.672%	$242.1974	$242.20	$242.20	$242.20
Purchase #2	$188.72	8.870%	$205.4595	$205.46	$205.45	$205.50
Purchase #3	$10.36	10.700%	$11.4685	$11.47	$11.45	$11.50
Purchase #4	$152.63	8.677%	$165.8737	$165.87	$165.85	$165.90
Purchase #5	$85.84	12.453%	$96.5297	$96.53	$96.55	$96.50
Purchase #6	$138.35	5.764%	$146.3245	$146.32	$146.30	$146.30
Purchase #7	$27.78	6.307%	$29.5321	$29.53	$29.55	$29.50
7 purchase totals =	$828.62		$897.3854	$897.38	$897.35	$897.40