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	$95.55	8.415%	$103.5905	$103.59	$103.60	$103.60
Purchase #2	$81.67	6.286%	$86.8038	$86.80	$86.80	$86.80
Purchase #3	$233.66	13.665%	$265.5896	$265.59	$265.60	$265.60
Purchase #4	$197.59	6.268%	$209.9749	$209.97	$209.95	$210.00
Purchase #5	$148.97	10.284%	$164.2901	$164.29	$164.30	$164.30
Purchase #6	$188.34	10.717%	$208.5244	$208.52	$208.50	$208.50
Purchase #7	$57.73	13.476%	$65.5097	$65.51	$65.50	$65.50
7 purchase totals =	$1,003.51		$1,104.2830	$1,104.27	$1,104.25	$1,104.30