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	$154.85	7.736%	$166.8292	$166.83	$166.85	$166.80
Purchase #2	$25.93	11.521%	$28.9174	$28.92	$28.90	$28.90
Purchase #3	$48.87	3.262%	$50.4641	$50.46	$50.45	$50.50
Purchase #4	$151.72	8.339%	$164.3719	$164.37	$164.35	$164.40
Purchase #5	$91.38	11.402%	$101.7991	$101.80	$101.80	$101.80
Purchase #6	$160.42	5.843%	$169.7933	$169.79	$169.80	$169.80
Purchase #7	$82.59	7.477%	$88.7653	$88.77	$88.75	$88.80
7 purchase totals =	$715.76		$770.9403	$770.94	$770.90	$771.00