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	$189.30	3.811%	$196.5142	$196.51	$196.50	$196.50
Purchase #2	$158.82	6.184%	$168.6414	$168.64	$168.65	$168.60
Purchase #3	$153.54	12.680%	$173.0089	$173.01	$173.00	$173.00
Purchase #4	$212.33	10.648%	$234.9389	$234.94	$234.95	$234.90
Purchase #5	$68.74	13.704%	$78.1601	$78.16	$78.15	$78.20
Purchase #6	$21.59	6.175%	$22.9232	$22.92	$22.90	$22.90
Purchase #7	$119.97	8.523%	$130.195	$130.20	$130.20	$130.20
7 purchase totals =	$924.29		$1,004.3817	$1,004.38	$1,004.35	$1,004.30