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	$213.29	7.425%	$229.1268	$229.13	$229.15	$229.10
Purchase #2	$53.51	10.811%	$59.295	$59.30	$59.30	$59.30
Purchase #3	$27.85	10.511%	$30.7773	$30.78	$30.80	$30.80
Purchase #4	$47.69	5.133%	$50.1379	$50.14	$50.15	$50.10
Purchase #5	$24.47	13.657%	$27.8119	$27.81	$27.80	$27.80
Purchase #6	$82.26	7.499%	$88.4287	$88.43	$88.45	$88.40
Purchase #7	$156.45	3.866%	$162.4984	$162.50	$162.50	$162.50
7 purchase totals =	$605.52		$648.0760	$648.09	$648.15	$648.00