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	$190.90	13.159%	$216.0205	$216.02	$216.00	$216.00
Purchase #2	$57.30	3.148%	$59.1038	$59.10	$59.10	$59.10
Purchase #3	$152.32	7.724%	$164.0852	$164.09	$164.10	$164.10
Purchase #4	$115.45	9.110%	$125.9675	$125.97	$125.95	$126.00
Purchase #5	$161.51	4.535%	$168.8345	$168.83	$168.85	$168.80
Purchase #6	$31.61	8.785%	$34.3869	$34.39	$34.40	$34.40
Purchase #7	$159.43	3.601%	$165.1711	$165.17	$165.15	$165.20
7 purchase totals =	$868.52		$933.5695	$933.57	$933.55	$933.60