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	$19.60	11.222%	$21.7995	$21.80	$21.80	$21.80
Purchase #2	$246.99	11.168%	$274.5738	$274.57	$274.55	$274.60
Purchase #3	$14.49	7.390%	$15.5608	$15.56	$15.55	$15.60
Purchase #4	$35.50	4.837%	$37.2171	$37.22	$37.20	$37.20
Purchase #5	$184.82	7.337%	$198.3802	$198.38	$198.40	$198.40
Purchase #6	$239.82	3.778%	$248.8804	$248.88	$248.90	$248.90
Purchase #7	$241.56	3.642%	$250.3576	$250.36	$250.35	$250.40
7 purchase totals =	$982.78		$1,046.7694	$1,046.77	$1,046.75	$1,046.90