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	$180.76	6.697%	$192.8655	$192.87	$192.85	$192.90
Purchase #2	$138.59	13.651%	$157.5089	$157.51	$157.50	$157.50
Purchase #3	$142.38	11.159%	$158.2682	$158.27	$158.25	$158.30
Purchase #4	$250.89	8.781%	$272.9207	$272.92	$272.90	$272.90
Purchase #5	$210.65	6.173%	$223.6534	$223.65	$223.65	$223.70
Purchase #6	$88.97	7.279%	$95.4461	$95.45	$95.45	$95.40
Purchase #7	$149.90	4.212%	$156.2138	$156.21	$156.20	$156.20
7 purchase totals =	$1,162.14		$1,256.8766	$1,256.88	$1,256.80	$1,256.90