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	$127.61	13.330%	$144.6204	$144.62	$144.60	$144.60
Purchase #2	$131.44	12.571%	$147.9633	$147.96	$147.95	$148.00
Purchase #3	$162.83	11.237%	$181.1272	$181.13	$181.15	$181.10
Purchase #4	$57.27	7.667%	$61.6609	$61.66	$61.65	$61.70
Purchase #5	$177.93	10.177%	$196.0379	$196.04	$196.05	$196.00
Purchase #6	$109.79	7.197%	$117.6916	$117.69	$117.70	$117.70
Purchase #7	$111.28	6.854%	$118.9071	$118.91	$118.90	$118.90
7 purchase totals =	$878.15		$968.0084	$968.01	$968.00	$968.00