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	$40.96	7.299%	$43.9497	$43.95	$43.95	$43.90
Purchase #2	$82.86	6.770%	$88.4696	$88.47	$88.45	$88.50
Purchase #3	$61.49	5.658%	$64.9691	$64.97	$64.95	$65.00
Purchase #4	$44.27	13.719%	$50.3434	$50.34	$50.35	$50.30
Purchase #5	$12.57	5.791%	$13.2979	$13.30	$13.30	$13.30
Purchase #6	$74.55	10.285%	$82.2175	$82.22	$82.20	$82.20
Purchase #7	$77.99	11.167%	$86.6991	$86.70	$86.70	$86.70
7 purchase totals =	$394.69		$429.9463	$429.95	$429.90	$429.90