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	$124.65	7.566%	$134.081	$134.08	$134.10	$134.10
Purchase #2	$86.42	4.570%	$90.3694	$90.37	$90.35	$90.40
Purchase #3	$92.71	9.685%	$101.689	$101.69	$101.70	$101.70
Purchase #4	$64.91	9.209%	$70.8876	$70.89	$70.90	$70.90
Purchase #5	$35.68	13.235%	$40.4022	$40.40	$40.40	$40.40
Purchase #6	$199.75	6.755%	$213.2431	$213.24	$213.25	$213.20
Purchase #7	$37.60	8.261%	$40.7061	$40.71	$40.70	$40.70
7 purchase totals =	$641.72		$691.3784	$691.38	$691.40	$691.40