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	$40.79	7.859%	$43.9957	$44.00	$44.00	$44.00
Purchase #2	$144.73	4.497%	$151.2385	$151.24	$151.25	$151.20
Purchase #3	$151.52	5.714%	$160.1779	$160.18	$160.20	$160.20
Purchase #4	$229.53	6.693%	$244.8924	$244.89	$244.90	$244.90
Purchase #5	$224.47	6.674%	$239.4511	$239.45	$239.45	$239.50
Purchase #6	$81.89	4.511%	$85.5841	$85.58	$85.60	$85.60
Purchase #7	$162.79	6.250%	$172.9644	$172.96	$172.95	$173.00
7 purchase totals =	$1,035.72		$1,098.3041	$1,098.30	$1,098.35	$1,098.40