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	$92.50	11.784%	$103.4002	$103.40	$103.40	$103.40
Purchase #2	$32.32	5.109%	$33.9712	$33.97	$33.95	$34.00
Purchase #3	$37.45	13.701%	$42.581	$42.58	$42.60	$42.60
Purchase #4	$221.69	7.164%	$237.5719	$237.57	$237.55	$237.60
Purchase #5	$57.61	9.254%	$62.9412	$62.94	$62.95	$62.90
Purchase #6	$228.86	9.519%	$250.6452	$250.65	$250.65	$250.60
Purchase #7	$27.35	7.707%	$29.4579	$29.46	$29.45	$29.50
7 purchase totals =	$697.78		$760.5686	$760.57	$760.55	$760.60