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	$24.63	3.341%	$25.4529	$25.45	$25.45	$25.50
Purchase #2	$177.97	4.142%	$185.3415	$185.34	$185.35	$185.30
Purchase #3	$216.74	5.377%	$228.3941	$228.39	$228.40	$228.40
Purchase #4	$153.30	13.150%	$173.459	$173.46	$173.45	$173.50
Purchase #5	$79.97	12.468%	$89.9407	$89.94	$89.95	$89.90
Purchase #6	$188.82	11.443%	$210.4267	$210.43	$210.45	$210.40
Purchase #7	$173.91	8.240%	$188.2402	$188.24	$188.25	$188.20
7 purchase totals =	$1,015.34		$1,101.2551	$1,101.25	$1,101.30	$1,101.20