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	$102.64	9.117%	$111.9977	$112.00	$112.00	$112.00
Purchase #2	$133.69	4.361%	$139.5202	$139.52	$139.50	$139.50
Purchase #3	$203.67	5.796%	$215.4747	$215.47	$215.45	$215.50
Purchase #4	$187.64	6.284%	$199.4313	$199.43	$199.45	$199.40
Purchase #5	$220.53	5.787%	$233.2921	$233.29	$233.30	$233.30
Purchase #6	$222.64	8.218%	$240.9366	$240.94	$240.95	$240.90
Purchase #7	$25.44	9.405%	$27.8326	$27.83	$27.85	$27.80
7 purchase totals =	$1,096.25		$1,168.4852	$1,168.48	$1,168.50	$1,168.40