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	$101.50	11.203%	$112.871	$112.87	$112.85	$112.90
Purchase #2	$132.73	5.810%	$140.4416	$140.44	$140.45	$140.40
Purchase #3	$219.60	9.862%	$241.257	$241.26	$241.25	$241.30
Purchase #4	$189.35	11.464%	$211.0571	$211.06	$211.05	$211.10
Purchase #5	$135.87	13.221%	$153.8334	$153.83	$153.85	$153.80
Purchase #6	$100.65	9.209%	$109.9189	$109.92	$109.90	$109.90
Purchase #7	$107.85	8.413%	$116.9234	$116.92	$116.90	$116.90
7 purchase totals =	$987.55		$1,086.3024	$1,086.30	$1,086.25	$1,086.30