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	$213.53	13.128%	$241.5622	$241.56	$241.55	$241.60
Purchase #2	$58.81	9.647%	$64.4834	$64.48	$64.50	$64.50
Purchase #3	$154.50	4.352%	$161.2238	$161.22	$161.20	$161.20
Purchase #4	$231.61	13.725%	$263.3985	$263.40	$263.40	$263.40
Purchase #5	$222.82	4.825%	$233.5711	$233.57	$233.55	$233.60
Purchase #6	$133.81	12.192%	$150.1241	$150.12	$150.10	$150.10
Purchase #7	$99.56	13.624%	$113.1241	$113.12	$113.10	$113.10
7 purchase totals =	$1,114.64		$1,227.4872	$1,227.47	$1,227.40	$1,227.50