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	$129.55	9.372%	$141.6914	$141.69	$141.70	$141.70
Purchase #2	$115.41	4.475%	$120.5746	$120.57	$120.55	$120.60
Purchase #3	$112.79	9.245%	$123.2174	$123.22	$123.20	$123.20
Purchase #4	$224.61	8.816%	$244.4116	$244.41	$244.40	$244.40
Purchase #5	$128.42	11.518%	$143.2114	$143.21	$143.20	$143.20
Purchase #6	$173.54	3.357%	$179.3657	$179.37	$179.35	$179.40
Purchase #7	$118.54	13.401%	$134.4255	$134.43	$134.45	$134.40
7 purchase totals =	$1,002.86		$1,086.8976	$1,086.90	$1,086.85	$1,086.90