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	$83.72	11.423%	$93.2833	$93.28	$93.30	$93.30
Purchase #2	$200.41	12.694%	$225.85	$225.85	$225.85	$225.90
Purchase #3	$135.28	6.564%	$144.1598	$144.16	$144.15	$144.20
Purchase #4	$97.45	12.285%	$109.4217	$109.42	$109.40	$109.40
Purchase #5	$61.53	9.345%	$67.28	$67.28	$67.30	$67.30
Purchase #6	$74.62	11.247%	$83.0125	$83.01	$83.00	$83.00
Purchase #7	$148.32	3.529%	$153.5542	$153.55	$153.55	$153.60
7 purchase totals =	$801.33		$876.5615	$876.55	$876.55	$876.70