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	$170.29	9.196%	$185.9499	$185.95	$185.95	$185.90
Purchase #2	$222.32	7.329%	$238.6138	$238.61	$238.60	$238.60
Purchase #3	$162.44	3.727%	$168.4941	$168.49	$168.50	$168.50
Purchase #4	$195.71	10.128%	$215.5315	$215.53	$215.55	$215.50
Purchase #5	$61.82	6.692%	$65.957	$65.96	$65.95	$66.00
Purchase #6	$55.86	13.443%	$63.3693	$63.37	$63.35	$63.40
Purchase #7	$46.95	4.476%	$49.0515	$49.05	$49.05	$49.10
7 purchase totals =	$915.39		$986.9671	$986.96	$986.95	$987.00