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	$169.34	12.216%	$190.0266	$190.03	$190.05	$190.00
Purchase #2	$113.85	7.558%	$122.4548	$122.45	$122.45	$122.50
Purchase #3	$216.54	13.105%	$244.9176	$244.92	$244.90	$244.90
Purchase #4	$47.50	5.575%	$50.1481	$50.15	$50.15	$50.10
Purchase #5	$109.28	8.394%	$118.453	$118.45	$118.45	$118.50
Purchase #6	$241.43	7.658%	$259.9187	$259.92	$259.90	$259.90
Purchase #7	$68.80	13.815%	$78.3047	$78.30	$78.30	$78.30
7 purchase totals =	$966.74		$1,064.2235	$1,064.22	$1,064.20	$1,064.20