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	$227.90	4.513%	$238.1851	$238.19	$238.20	$238.20
Purchase #2	$60.58	12.819%	$68.3458	$68.35	$68.35	$68.30
Purchase #3	$143.69	8.763%	$156.2816	$156.28	$156.30	$156.30
Purchase #4	$146.98	12.526%	$165.3907	$165.39	$165.40	$165.40
Purchase #5	$42.27	13.198%	$47.8488	$47.85	$47.85	$47.80
Purchase #6	$51.61	12.163%	$57.8873	$57.89	$57.90	$57.90
Purchase #7	$34.59	11.566%	$38.5907	$38.59	$38.60	$38.60
7 purchase totals =	$707.62		$772.5300	$772.54	$772.60	$772.50