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	$155.26	9.439%	$169.915	$169.92	$169.90	$169.90
Purchase #2	$48.92	12.690%	$55.1279	$55.13	$55.15	$55.10
Purchase #3	$103.61	5.334%	$109.1366	$109.14	$109.15	$109.10
Purchase #4	$138.44	12.306%	$155.4764	$155.48	$155.50	$155.50
Purchase #5	$143.31	8.471%	$155.4498	$155.45	$155.45	$155.40
Purchase #6	$134.70	7.297%	$144.5291	$144.53	$144.55	$144.50
Purchase #7	$196.77	11.597%	$219.5894	$219.59	$219.60	$219.60
7 purchase totals =	$921.01		$1,009.2242	$1,009.24	$1,009.30	$1,009.10