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	$92.27	6.491%	$98.2592	$98.26	$98.25	$98.30
Purchase #2	$56.51	5.202%	$59.4497	$59.45	$59.45	$59.40
Purchase #3	$135.93	12.562%	$153.0055	$153.01	$153.00	$153.00
Purchase #4	$157.68	4.752%	$165.173	$165.17	$165.15	$165.20
Purchase #5	$210.75	7.178%	$225.8776	$225.88	$225.90	$225.90
Purchase #6	$80.36	12.129%	$90.1069	$90.11	$90.10	$90.10
Purchase #7	$142.50	8.381%	$154.4429	$154.44	$154.45	$154.40
7 purchase totals =	$876.00		$946.3148	$946.32	$946.30	$946.30