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	$99.85	12.144%	$111.9758	$111.98	$112.00	$112.00
Purchase #2	$198.78	5.153%	$209.0231	$209.02	$209.00	$209.00
Purchase #3	$37.66	8.873%	$41.0016	$41.00	$41.00	$41.00
Purchase #4	$164.55	5.556%	$173.6924	$173.69	$173.70	$173.70
Purchase #5	$42.77	8.670%	$46.4782	$46.48	$46.50	$46.50
Purchase #6	$20.72	12.852%	$23.3829	$23.38	$23.40	$23.40
Purchase #7	$94.49	6.709%	$100.8293	$100.83	$100.85	$100.80
7 purchase totals =	$658.82		$706.3833	$706.38	$706.45	$706.40