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	$132.76	13.103%	$150.1555	$150.16	$150.15	$150.20
Purchase #2	$196.83	9.542%	$215.6115	$215.61	$215.60	$215.60
Purchase #3	$75.67	4.392%	$78.9934	$78.99	$79.00	$79.00
Purchase #4	$18.93	7.269%	$20.306	$20.31	$20.30	$20.30
Purchase #5	$181.30	5.637%	$191.5199	$191.52	$191.50	$191.50
Purchase #6	$159.37	6.509%	$169.7434	$169.74	$169.75	$169.70
Purchase #7	$69.88	12.122%	$78.3509	$78.35	$78.35	$78.40
7 purchase totals =	$834.74		$904.6806	$904.68	$904.65	$904.70