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	$207.56	8.244%	$224.6712	$224.67	$224.65	$224.70
Purchase #2	$87.85	3.394%	$90.8316	$90.83	$90.85	$90.80
Purchase #3	$241.94	9.874%	$265.8292	$265.83	$265.85	$265.80
Purchase #4	$239.87	13.423%	$272.0678	$272.07	$272.05	$272.10
Purchase #5	$87.54	13.547%	$99.399	$99.40	$99.40	$99.40
Purchase #6	$241.51	13.547%	$274.2274	$274.23	$274.25	$274.20
Purchase #7	$159.77	7.413%	$171.6138	$171.61	$171.60	$171.60
7 purchase totals =	$1,266.04		$1,398.6400	$1,398.64	$1,398.65	$1,398.60