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	$165.61	4.388%	$172.877	$172.88	$172.90	$172.90
Purchase #2	$159.57	3.117%	$164.5438	$164.54	$164.55	$164.50
Purchase #3	$126.31	10.740%	$139.8757	$139.88	$139.90	$139.90
Purchase #4	$57.57	13.554%	$65.373	$65.37	$65.35	$65.40
Purchase #5	$90.59	5.414%	$95.4945	$95.49	$95.50	$95.50
Purchase #6	$62.66	10.758%	$69.401	$69.40	$69.40	$69.40
Purchase #7	$9.98	6.546%	$10.6333	$10.63	$10.65	$10.60
7 purchase totals =	$672.29		$718.1983	$718.19	$718.25	$718.20