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	$33.35	7.163%	$35.7389	$35.74	$35.75	$35.70
Purchase #2	$42.64	6.865%	$45.5672	$45.57	$45.55	$45.60
Purchase #3	$16.42	12.184%	$18.4206	$18.42	$18.40	$18.40
Purchase #4	$65.58	11.172%	$72.9066	$72.91	$72.90	$72.90
Purchase #5	$106.38	10.250%	$117.284	$117.28	$117.30	$117.30
Purchase #6	$217.56	9.288%	$237.767	$237.77	$237.75	$237.80
Purchase #7	$11.41	13.383%	$12.937	$12.94	$12.95	$12.90
7 purchase totals =	$493.34		$540.6213	$540.63	$540.60	$540.60