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	$218.92	11.511%	$244.1199	$244.12	$244.10	$244.10
Purchase #2	$94.67	5.512%	$99.8882	$99.89	$99.90	$99.90
Purchase #3	$57.47	13.292%	$65.1089	$65.11	$65.10	$65.10
Purchase #4	$113.68	5.408%	$119.8278	$119.83	$119.85	$119.80
Purchase #5	$192.90	3.770%	$200.1723	$200.17	$200.15	$200.20
Purchase #6	$151.94	5.597%	$160.4441	$160.44	$160.45	$160.40
Purchase #7	$217.70	13.409%	$246.8914	$246.89	$246.90	$246.90
7 purchase totals =	$1,047.28		$1,136.4526	$1,136.45	$1,136.45	$1,136.40