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	$125.56	4.513%	$131.2265	$131.23	$131.25	$131.20
Purchase #2	$142.94	6.648%	$152.4427	$152.44	$152.45	$152.40
Purchase #3	$15.76	11.133%	$17.5146	$17.51	$17.50	$17.50
Purchase #4	$133.92	5.665%	$141.5066	$141.51	$141.50	$141.50
Purchase #5	$63.32	11.316%	$70.4853	$70.49	$70.50	$70.50
Purchase #6	$60.42	4.635%	$63.2205	$63.22	$63.20	$63.20
Purchase #7	$131.80	4.604%	$137.8681	$137.87	$137.85	$137.90
7 purchase totals =	$673.72		$714.2643	$714.27	$714.25	$714.20