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	$96.96	11.436%	$108.0483	$108.05	$108.05	$108.00
Purchase #2	$112.69	11.612%	$125.7756	$125.78	$125.80	$125.80
Purchase #3	$179.45	3.852%	$186.3624	$186.36	$186.35	$186.40
Purchase #4	$247.76	3.706%	$256.942	$256.94	$256.95	$256.90
Purchase #5	$139.89	8.670%	$152.0185	$152.02	$152.00	$152.00
Purchase #6	$66.73	8.332%	$72.2899	$72.29	$72.30	$72.30
Purchase #7	$226.54	6.169%	$240.5153	$240.52	$240.50	$240.50
7 purchase totals =	$1,070.02		$1,141.9520	$1,141.96	$1,141.95	$1,141.90