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	$243.73	6.307%	$259.1021	$259.10	$259.10	$259.10
Purchase #2	$10.52	3.223%	$10.8591	$10.86	$10.85	$10.90
Purchase #3	$31.61	11.479%	$35.2385	$35.24	$35.25	$35.20
Purchase #4	$183.29	9.600%	$200.8858	$200.89	$200.90	$200.90
Purchase #5	$146.44	7.241%	$157.0437	$157.04	$157.05	$157.00
Purchase #6	$52.63	13.578%	$59.7761	$59.78	$59.80	$59.80
Purchase #7	$201.91	10.671%	$223.4558	$223.46	$223.45	$223.50
7 purchase totals =	$870.13		$946.3611	$946.37	$946.40	$946.40