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	$67.65	7.587%	$72.7826	$72.78	$72.80	$72.80
Purchase #2	$46.71	5.443%	$49.2524	$49.25	$49.25	$49.30
Purchase #3	$34.28	3.868%	$35.606	$35.61	$35.60	$35.60
Purchase #4	$12.48	13.143%	$14.1202	$14.12	$14.10	$14.10
Purchase #5	$238.41	8.520%	$258.7225	$258.72	$258.70	$258.70
Purchase #6	$159.52	7.757%	$171.894	$171.89	$171.90	$171.90
Purchase #7	$64.77	12.732%	$73.0165	$73.02	$73.00	$73.00
7 purchase totals =	$623.82		$675.3942	$675.39	$675.35	$675.40