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	$99.37	7.537%	$106.8595	$106.86	$106.85	$106.90
Purchase #2	$235.49	5.628%	$248.7434	$248.74	$248.75	$248.70
Purchase #3	$247.42	7.277%	$265.4248	$265.42	$265.40	$265.40
Purchase #4	$156.86	13.664%	$178.2934	$178.29	$178.30	$178.30
Purchase #5	$121.80	4.704%	$127.5295	$127.53	$127.55	$127.50
Purchase #6	$77.93	5.801%	$82.4507	$82.45	$82.45	$82.50
Purchase #7	$184.47	13.629%	$209.6114	$209.61	$209.60	$209.60
7 purchase totals =	$1,123.34		$1,218.9127	$1,218.90	$1,218.90	$1,218.90