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	$90.81	9.492%	$99.4297	$99.43	$99.45	$99.40
Purchase #2	$117.45	5.287%	$123.6596	$123.66	$123.65	$123.70
Purchase #3	$143.67	4.342%	$149.9082	$149.91	$149.90	$149.90
Purchase #4	$52.26	10.472%	$57.7327	$57.73	$57.75	$57.70
Purchase #5	$149.45	8.409%	$162.0173	$162.02	$162.00	$162.00
Purchase #6	$223.39	13.805%	$254.229	$254.23	$254.25	$254.20
Purchase #7	$227.36	5.451%	$239.7534	$239.75	$239.75	$239.80
7 purchase totals =	$1,004.39		$1,086.7299	$1,086.73	$1,086.75	$1,086.70