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	$83.67	10.396%	$92.3683	$92.37	$92.35	$92.40
Purchase #2	$248.77	10.407%	$274.6595	$274.66	$274.65	$274.70
Purchase #3	$103.90	9.440%	$113.7082	$113.71	$113.70	$113.70
Purchase #4	$13.60	8.234%	$14.7198	$14.72	$14.70	$14.70
Purchase #5	$216.78	3.104%	$223.5089	$223.51	$223.50	$223.50
Purchase #6	$55.92	12.404%	$62.8563	$62.86	$62.85	$62.90
Purchase #7	$17.81	13.160%	$20.1538	$20.15	$20.15	$20.20
7 purchase totals =	$740.45		$801.9748	$801.98	$801.90	$802.10