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	$101.99	9.156%	$111.3282	$111.33	$111.35	$111.30
Purchase #2	$82.59	7.273%	$88.5968	$88.60	$88.60	$88.60
Purchase #3	$54.96	11.388%	$61.2188	$61.22	$61.20	$61.20
Purchase #4	$74.99	9.761%	$82.3098	$82.31	$82.30	$82.30
Purchase #5	$151.34	3.498%	$156.6339	$156.63	$156.65	$156.60
Purchase #6	$204.80	10.482%	$226.2671	$226.27	$226.25	$226.30
Purchase #7	$83.76	8.480%	$90.8628	$90.86	$90.85	$90.90
7 purchase totals =	$754.43		$817.2174	$817.22	$817.20	$817.20