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	$97.79	8.188%	$105.797	$105.80	$105.80	$105.80
Purchase #2	$121.90	7.563%	$131.1193	$131.12	$131.10	$131.10
Purchase #3	$202.43	5.666%	$213.8997	$213.90	$213.90	$213.90
Purchase #4	$166.90	10.475%	$184.3828	$184.38	$184.40	$184.40
Purchase #5	$200.30	5.146%	$210.6074	$210.61	$210.60	$210.60
Purchase #6	$74.65	11.296%	$83.0825	$83.08	$83.10	$83.10
Purchase #7	$134.45	10.324%	$148.3306	$148.33	$148.35	$148.30
7 purchase totals =	$998.42		$1,077.2193	$1,077.22	$1,077.25	$1,077.20