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	$184.86	5.491%	$195.0107	$195.01	$195.00	$195.00
Purchase #2	$222.69	12.178%	$249.8092	$249.81	$249.80	$249.80
Purchase #3	$107.92	10.200%	$118.9278	$118.93	$118.95	$118.90
Purchase #4	$95.83	10.124%	$105.5318	$105.53	$105.55	$105.50
Purchase #5	$83.56	3.162%	$86.2022	$86.20	$86.20	$86.20
Purchase #6	$80.58	7.678%	$86.7669	$86.77	$86.75	$86.80
Purchase #7	$103.46	5.408%	$109.0551	$109.06	$109.05	$109.10
7 purchase totals =	$878.90		$951.3037	$951.31	$951.30	$951.30