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	$222.69	11.743%	$248.8405	$248.84	$248.85	$248.80
Purchase #2	$96.29	13.672%	$109.4548	$109.45	$109.45	$109.50
Purchase #3	$208.82	6.714%	$222.8402	$222.84	$222.85	$222.80
Purchase #4	$17.49	7.231%	$18.7547	$18.75	$18.75	$18.80
Purchase #5	$114.34	10.587%	$126.4452	$126.45	$126.45	$126.40
Purchase #6	$43.91	13.626%	$49.8932	$49.89	$49.90	$49.90
Purchase #7	$242.73	9.442%	$265.6486	$265.65	$265.65	$265.60
7 purchase totals =	$946.27		$1,041.8772	$1,041.87	$1,041.90	$1,041.80