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	$150.92	11.544%	$168.3422	$168.34	$168.35	$168.30
Purchase #2	$64.64	4.520%	$67.5617	$67.56	$67.55	$67.60
Purchase #3	$154.88	11.514%	$172.7129	$172.71	$172.70	$172.70
Purchase #4	$210.87	12.660%	$237.5661	$237.57	$237.55	$237.60
Purchase #5	$160.69	11.103%	$178.5314	$178.53	$178.55	$178.50
Purchase #6	$175.37	11.393%	$195.3499	$195.35	$195.35	$195.30
Purchase #7	$58.85	11.293%	$65.4959	$65.50	$65.50	$65.50
7 purchase totals =	$976.22		$1,085.5601	$1,085.56	$1,085.55	$1,085.50