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	$241.56	10.284%	$266.402	$266.40	$266.40	$266.40
Purchase #2	$37.38	8.578%	$40.5865	$40.59	$40.60	$40.60
Purchase #3	$191.87	13.595%	$217.9547	$217.95	$217.95	$218.00
Purchase #4	$134.27	7.120%	$143.83	$143.83	$143.85	$143.80
Purchase #5	$9.90	4.339%	$10.3296	$10.33	$10.35	$10.30
Purchase #6	$90.31	10.286%	$99.5993	$99.60	$99.60	$99.60
Purchase #7	$208.50	11.309%	$232.0793	$232.08	$232.10	$232.10
7 purchase totals =	$913.79		$1,010.7814	$1,010.78	$1,010.85	$1,010.80