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	$103.29	13.507%	$117.2414	$117.24	$117.25	$117.20
Purchase #2	$42.95	6.722%	$45.8371	$45.84	$45.85	$45.80
Purchase #3	$218.90	4.425%	$228.5863	$228.59	$228.60	$228.60
Purchase #4	$96.73	7.572%	$104.0544	$104.05	$104.05	$104.10
Purchase #5	$40.84	4.504%	$42.6794	$42.68	$42.70	$42.70
Purchase #6	$238.89	10.720%	$264.499	$264.50	$264.50	$264.50
Purchase #7	$45.29	8.622%	$49.1949	$49.19	$49.20	$49.20
7 purchase totals =	$786.89		$852.0925	$852.09	$852.15	$852.10