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	$130.26	5.132%	$136.9449	$136.94	$136.95	$136.90
Purchase #2	$87.28	3.313%	$90.1716	$90.17	$90.15	$90.20
Purchase #3	$244.45	8.762%	$265.8687	$265.87	$265.85	$265.90
Purchase #4	$29.39	9.396%	$32.1515	$32.15	$32.15	$32.20
Purchase #5	$172.30	3.362%	$178.0927	$178.09	$178.10	$178.10
Purchase #6	$111.35	4.502%	$116.363	$116.36	$116.35	$116.40
Purchase #7	$234.51	4.728%	$245.5976	$245.60	$245.60	$245.60
7 purchase totals =	$1,009.54		$1,065.1900	$1,065.18	$1,065.15	$1,065.30