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	$62.99	7.179%	$67.5121	$67.51	$67.50	$67.50
Purchase #2	$82.35	8.607%	$89.4379	$89.44	$89.45	$89.40
Purchase #3	$235.55	7.468%	$253.1409	$253.14	$253.15	$253.10
Purchase #4	$152.78	13.622%	$173.5917	$173.59	$173.60	$173.60
Purchase #5	$163.80	5.450%	$172.7271	$172.73	$172.75	$172.70
Purchase #6	$21.98	9.145%	$23.9901	$23.99	$24.00	$24.00
Purchase #7	$226.46	6.512%	$241.2071	$241.21	$241.20	$241.20
7 purchase totals =	$945.91		$1,021.6069	$1,021.61	$1,021.65	$1,021.50