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	$133.86	13.864%	$152.4184	$152.42	$152.40	$152.40
Purchase #2	$248.98	5.152%	$261.8074	$261.81	$261.80	$261.80
Purchase #3	$72.48	13.512%	$82.2735	$82.27	$82.25	$82.30
Purchase #4	$92.32	11.103%	$102.5703	$102.57	$102.55	$102.60
Purchase #5	$228.92	10.579%	$253.1374	$253.14	$253.15	$253.10
Purchase #6	$197.53	13.636%	$224.4652	$224.47	$224.45	$224.50
Purchase #7	$188.28	10.782%	$208.5803	$208.58	$208.60	$208.60
7 purchase totals =	$1,162.37		$1,285.2525	$1,285.26	$1,285.20	$1,285.30