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	$247.43	3.194%	$255.3329	$255.33	$255.35	$255.30
Purchase #2	$170.95	7.250%	$183.3439	$183.34	$183.35	$183.30
Purchase #3	$87.59	6.111%	$92.9426	$92.94	$92.95	$92.90
Purchase #4	$125.33	11.312%	$139.5073	$139.51	$139.50	$139.50
Purchase #5	$201.35	12.456%	$226.4302	$226.43	$226.45	$226.40
Purchase #6	$32.37	9.140%	$35.3286	$35.33	$35.35	$35.30
Purchase #7	$140.63	4.492%	$146.9471	$146.95	$146.95	$146.90
7 purchase totals =	$1,005.65		$1,079.8326	$1,079.83	$1,079.90	$1,079.60