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	$92.86	5.874%	$98.3146	$98.31	$98.30	$98.30
Purchase #2	$12.71	8.109%	$13.7407	$13.74	$13.75	$13.70
Purchase #3	$141.32	12.136%	$158.4706	$158.47	$158.45	$158.50
Purchase #4	$24.40	12.217%	$27.3809	$27.38	$27.40	$27.40
Purchase #5	$220.86	13.532%	$250.7468	$250.75	$250.75	$250.70
Purchase #6	$237.46	11.342%	$264.3927	$264.39	$264.40	$264.40
Purchase #7	$22.96	10.176%	$25.2964	$25.30	$25.30	$25.30
7 purchase totals =	$752.57		$838.3427	$838.34	$838.35	$838.30