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	$37.41	11.324%	$41.6463	$41.65	$41.65	$41.60
Purchase #2	$47.32	13.712%	$53.8085	$53.81	$53.80	$53.80
Purchase #3	$49.70	11.109%	$55.2212	$55.22	$55.20	$55.20
Purchase #4	$113.51	13.170%	$128.4593	$128.46	$128.45	$128.50
Purchase #5	$139.30	9.298%	$152.2521	$152.25	$152.25	$152.30
Purchase #6	$85.63	5.745%	$90.5494	$90.55	$90.55	$90.50
Purchase #7	$162.54	8.536%	$176.4144	$176.41	$176.40	$176.40
7 purchase totals =	$635.41		$698.3512	$698.35	$698.30	$698.30