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	$236.64	10.506%	$261.5014	$261.50	$261.50	$261.50
Purchase #2	$176.52	11.318%	$196.4985	$196.50	$196.50	$196.50
Purchase #3	$109.76	11.359%	$122.2276	$122.23	$122.25	$122.20
Purchase #4	$87.91	9.177%	$95.9775	$95.98	$96.00	$96.00
Purchase #5	$23.90	4.676%	$25.0176	$25.02	$25.00	$25.00
Purchase #6	$240.38	3.364%	$248.4664	$248.47	$248.45	$248.50
Purchase #7	$106.42	5.230%	$111.9858	$111.99	$112.00	$112.00
7 purchase totals =	$981.53		$1,061.6748	$1,061.69	$1,061.70	$1,061.70