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	$197.83	12.273%	$222.1097	$222.11	$222.10	$222.10
Purchase #2	$185.36	3.668%	$192.159	$192.16	$192.15	$192.20
Purchase #3	$77.57	13.450%	$88.0032	$88.00	$88.00	$88.00
Purchase #4	$104.83	3.404%	$108.3984	$108.40	$108.40	$108.40
Purchase #5	$39.41	10.171%	$43.4184	$43.42	$43.40	$43.40
Purchase #6	$81.71	9.472%	$89.4496	$89.45	$89.45	$89.40
Purchase #7	$9.44	12.248%	$10.5962	$10.60	$10.60	$10.60
7 purchase totals =	$696.15		$754.1345	$754.14	$754.10	$754.10