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	$22.76	10.133%	$25.0663	$25.07	$25.05	$25.10
Purchase #2	$215.63	6.419%	$229.4713	$229.47	$229.45	$229.50
Purchase #3	$100.83	10.766%	$111.6854	$111.69	$111.70	$111.70
Purchase #4	$56.48	3.589%	$58.5071	$58.51	$58.50	$58.50
Purchase #5	$126.33	11.854%	$141.3052	$141.31	$141.30	$141.30
Purchase #6	$121.40	4.210%	$126.5109	$126.51	$126.50	$126.50
Purchase #7	$206.72	13.542%	$234.714	$234.71	$234.70	$234.70
7 purchase totals =	$850.15		$927.2602	$927.27	$927.20	$927.30