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	$144.39	8.131%	$156.1304	$156.13	$156.15	$156.10
Purchase #2	$39.38	13.362%	$44.642	$44.64	$44.65	$44.60
Purchase #3	$144.29	5.194%	$151.7844	$151.78	$151.80	$151.80
Purchase #4	$73.55	13.622%	$83.569	$83.57	$83.55	$83.60
Purchase #5	$44.31	10.556%	$48.9874	$48.99	$49.00	$49.00
Purchase #6	$204.70	11.855%	$228.9672	$228.97	$228.95	$229.00
Purchase #7	$53.92	9.870%	$59.2419	$59.24	$59.25	$59.20
7 purchase totals =	$704.54		$773.3223	$773.32	$773.35	$773.30