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	$104.74	11.493%	$116.7778	$116.78	$116.80	$116.80
Purchase #2	$33.36	10.175%	$36.7544	$36.75	$36.75	$36.80
Purchase #3	$14.71	5.157%	$15.4686	$15.47	$15.45	$15.50
Purchase #4	$128.71	13.530%	$146.1245	$146.12	$146.10	$146.10
Purchase #5	$110.77	5.352%	$116.6984	$116.70	$116.70	$116.70
Purchase #6	$237.56	5.398%	$250.3835	$250.38	$250.40	$250.40
Purchase #7	$118.61	7.550%	$127.5651	$127.57	$127.55	$127.60
7 purchase totals =	$748.46		$809.7723	$809.77	$809.75	$809.90