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	$145.85	12.643%	$164.2898	$164.29	$164.30	$164.30
Purchase #2	$33.45	9.175%	$36.519	$36.52	$36.50	$36.50
Purchase #3	$72.47	5.845%	$76.7059	$76.71	$76.70	$76.70
Purchase #4	$169.96	13.269%	$192.512	$192.51	$192.50	$192.50
Purchase #5	$152.55	5.193%	$160.4719	$160.47	$160.45	$160.50
Purchase #6	$250.75	5.471%	$264.4685	$264.47	$264.45	$264.50
Purchase #7	$166.51	12.300%	$186.9907	$186.99	$187.00	$187.00
7 purchase totals =	$991.54		$1,081.9578	$1,081.96	$1,081.90	$1,082.00