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	$82.28	8.105%	$88.9488	$88.95	$88.95	$88.90
Purchase #2	$74.83	9.609%	$82.0204	$82.02	$82.00	$82.00
Purchase #3	$153.81	3.231%	$158.7796	$158.78	$158.80	$158.80
Purchase #4	$164.78	10.213%	$181.609	$181.61	$181.60	$181.60
Purchase #5	$243.71	6.596%	$259.7851	$259.79	$259.80	$259.80
Purchase #6	$240.87	6.393%	$256.2688	$256.27	$256.25	$256.30
Purchase #7	$104.77	5.155%	$110.1709	$110.17	$110.15	$110.20
7 purchase totals =	$1,065.05		$1,137.5826	$1,137.59	$1,137.55	$1,137.60