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	$48.33	8.159%	$52.2732	$52.27	$52.25	$52.30
Purchase #2	$171.66	11.853%	$192.0069	$192.01	$192.00	$192.00
Purchase #3	$139.30	5.627%	$147.1384	$147.14	$147.15	$147.10
Purchase #4	$240.44	12.131%	$269.6078	$269.61	$269.60	$269.60
Purchase #5	$62.63	5.639%	$66.1617	$66.16	$66.15	$66.20
Purchase #6	$178.69	5.497%	$188.5126	$188.51	$188.50	$188.50
Purchase #7	$198.32	11.691%	$221.5056	$221.51	$221.50	$221.50
7 purchase totals =	$1,039.37		$1,137.2062	$1,137.21	$1,137.15	$1,137.20