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	$233.63	10.335%	$257.7757	$257.78	$257.80	$257.80
Purchase #2	$51.92	11.500%	$57.8908	$57.89	$57.90	$57.90
Purchase #3	$198.49	5.825%	$210.052	$210.05	$210.05	$210.10
Purchase #4	$58.53	6.640%	$62.4164	$62.42	$62.40	$62.40
Purchase #5	$198.77	6.232%	$211.1573	$211.16	$211.15	$211.20
Purchase #6	$223.30	7.849%	$240.8268	$240.83	$240.85	$240.80
Purchase #7	$95.38	9.338%	$104.2866	$104.29	$104.30	$104.30
7 purchase totals =	$1,060.02		$1,144.4056	$1,144.42	$1,144.45	$1,144.50