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	$51.97	13.700%	$59.0899	$59.09	$59.10	$59.10
Purchase #2	$234.86	10.861%	$260.3681	$260.37	$260.35	$260.40
Purchase #3	$5.61	12.503%	$6.3114	$6.31	$6.30	$6.30
Purchase #4	$220.92	5.704%	$233.5213	$233.52	$233.50	$233.50
Purchase #5	$215.39	13.552%	$244.5797	$244.58	$244.60	$244.60
Purchase #6	$203.58	12.736%	$229.5079	$229.51	$229.50	$229.50
Purchase #7	$180.82	4.738%	$189.3873	$189.39	$189.40	$189.40
7 purchase totals =	$1,113.15		$1,222.7656	$1,222.77	$1,222.75	$1,222.80