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	$214.66	4.552%	$224.4313	$224.43	$224.45	$224.40
Purchase #2	$135.57	7.756%	$146.0848	$146.08	$146.10	$146.10
Purchase #3	$67.94	11.446%	$75.7164	$75.72	$75.70	$75.70
Purchase #4	$71.27	7.292%	$76.467	$76.47	$76.45	$76.50
Purchase #5	$79.92	13.806%	$90.9538	$90.95	$90.95	$91.00
Purchase #6	$83.79	6.610%	$89.3285	$89.33	$89.35	$89.30
Purchase #7	$185.54	3.613%	$192.2436	$192.24	$192.25	$192.20
7 purchase totals =	$838.69		$895.2254	$895.22	$895.25	$895.20