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	$225.50	8.339%	$244.3044	$244.30	$244.30	$244.30
Purchase #2	$90.47	12.786%	$102.0375	$102.04	$102.05	$102.00
Purchase #3	$236.77	9.195%	$258.541	$258.54	$258.55	$258.50
Purchase #4	$176.27	5.475%	$185.9208	$185.92	$185.90	$185.90
Purchase #5	$41.66	7.117%	$44.6249	$44.62	$44.60	$44.60
Purchase #6	$28.90	9.332%	$31.5969	$31.60	$31.60	$31.60
Purchase #7	$201.34	13.500%	$228.5209	$228.52	$228.50	$228.50
7 purchase totals =	$1,000.91		$1,095.5464	$1,095.54	$1,095.50	$1,095.40