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	$37.63	13.862%	$42.8463	$42.85	$42.85	$42.80
Purchase #2	$50.73	6.158%	$53.854	$53.85	$53.85	$53.90
Purchase #3	$105.40	6.628%	$112.3859	$112.39	$112.40	$112.40
Purchase #4	$143.36	12.466%	$161.2313	$161.23	$161.25	$161.20
Purchase #5	$32.27	10.844%	$35.7694	$35.77	$35.75	$35.80
Purchase #6	$249.48	5.450%	$263.0767	$263.08	$263.10	$263.10
Purchase #7	$5.54	11.369%	$6.1698	$6.17	$6.15	$6.20
7 purchase totals =	$624.41		$675.3334	$675.34	$675.35	$675.40