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	$203.27	7.493%	$218.501	$218.50	$218.50	$218.50
Purchase #2	$130.80	4.273%	$136.3891	$136.39	$136.40	$136.40
Purchase #3	$132.51	12.619%	$149.2314	$149.23	$149.25	$149.20
Purchase #4	$27.47	4.124%	$28.6029	$28.60	$28.60	$28.60
Purchase #5	$114.48	11.172%	$127.2697	$127.27	$127.25	$127.30
Purchase #6	$109.25	7.617%	$117.5716	$117.57	$117.55	$117.60
Purchase #7	$235.57	4.554%	$246.2979	$246.30	$246.30	$246.30
7 purchase totals =	$953.35		$1,023.8636	$1,023.86	$1,023.85	$1,023.90