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	$34.92	5.865%	$36.9681	$36.97	$36.95	$37.00
Purchase #2	$32.98	4.441%	$34.4446	$34.44	$34.45	$34.40
Purchase #3	$100.36	8.712%	$109.1034	$109.10	$109.10	$109.10
Purchase #4	$243.31	3.757%	$252.4512	$252.45	$252.45	$252.50
Purchase #5	$250.56	10.661%	$277.2722	$277.27	$277.25	$277.30
Purchase #6	$188.72	4.168%	$196.5858	$196.59	$196.60	$196.60
Purchase #7	$172.32	10.812%	$190.9512	$190.95	$190.95	$191.00
7 purchase totals =	$1,023.17		$1,097.7765	$1,097.77	$1,097.75	$1,097.90