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	$49.36	4.194%	$51.4302	$51.43	$51.45	$51.40
Purchase #2	$150.28	3.470%	$155.4947	$155.49	$155.50	$155.50
Purchase #3	$55.33	7.104%	$59.2606	$59.26	$59.25	$59.30
Purchase #4	$47.51	11.794%	$53.1133	$53.11	$53.10	$53.10
Purchase #5	$197.81	7.762%	$213.164	$213.16	$213.15	$213.20
Purchase #6	$224.45	6.111%	$238.1661	$238.17	$238.15	$238.20
Purchase #7	$124.83	13.724%	$141.9617	$141.96	$141.95	$142.00
7 purchase totals =	$849.57		$912.5906	$912.58	$912.55	$912.70