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	$226.77	12.229%	$254.5017	$254.50	$254.50	$254.50
Purchase #2	$26.78	6.801%	$28.6013	$28.60	$28.60	$28.60
Purchase #3	$228.97	6.802%	$244.5445	$244.54	$244.55	$244.50
Purchase #4	$125.35	13.227%	$141.93	$141.93	$141.95	$141.90
Purchase #5	$66.86	9.333%	$73.1	$73.10	$73.10	$73.10
Purchase #6	$245.78	9.461%	$269.0332	$269.03	$269.05	$269.00
Purchase #7	$45.88	8.341%	$49.7069	$49.71	$49.70	$49.70
7 purchase totals =	$966.39		$1,061.4176	$1,061.41	$1,061.45	$1,061.30