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	$22.40	9.124%	$24.4438	$24.44	$24.45	$24.40
Purchase #2	$154.83	7.697%	$166.7473	$166.75	$166.75	$166.70
Purchase #3	$247.25	10.215%	$272.5066	$272.51	$272.50	$272.50
Purchase #4	$92.50	11.309%	$102.9608	$102.96	$102.95	$103.00
Purchase #5	$109.89	11.678%	$122.723	$122.72	$122.70	$122.70
Purchase #6	$172.94	13.514%	$196.3111	$196.31	$196.30	$196.30
Purchase #7	$25.83	9.413%	$28.2614	$28.26	$28.25	$28.30
7 purchase totals =	$825.64		$913.9540	$913.95	$913.90	$913.90