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	$89.50	8.343%	$96.967	$96.97	$96.95	$97.00
Purchase #2	$146.90	5.812%	$155.4378	$155.44	$155.45	$155.40
Purchase #3	$164.51	4.178%	$171.3832	$171.38	$171.40	$171.40
Purchase #4	$30.46	6.302%	$32.3796	$32.38	$32.40	$32.40
Purchase #5	$34.67	7.468%	$37.2592	$37.26	$37.25	$37.30
Purchase #6	$208.58	12.393%	$234.4293	$234.43	$234.45	$234.40
Purchase #7	$101.73	9.493%	$111.3872	$111.39	$111.40	$111.40
7 purchase totals =	$776.35		$839.2433	$839.25	$839.30	$839.30