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	$60.59	6.275%	$64.392	$64.39	$64.40	$64.40
Purchase #2	$115.27	11.578%	$128.616	$128.62	$128.60	$128.60
Purchase #3	$31.79	12.273%	$35.6916	$35.69	$35.70	$35.70
Purchase #4	$13.41	11.495%	$14.9515	$14.95	$14.95	$15.00
Purchase #5	$147.80	13.569%	$167.855	$167.86	$167.85	$167.90
Purchase #6	$112.27	9.726%	$123.1894	$123.19	$123.20	$123.20
Purchase #7	$186.28	3.405%	$192.6228	$192.62	$192.60	$192.60
7 purchase totals =	$667.41		$727.3183	$727.32	$727.30	$727.40