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	$88.95	8.498%	$96.509	$96.51	$96.50	$96.50
Purchase #2	$134.82	12.785%	$152.0567	$152.06	$152.05	$152.10
Purchase #3	$36.86	9.757%	$40.4564	$40.46	$40.45	$40.50
Purchase #4	$87.53	13.518%	$99.3623	$99.36	$99.35	$99.40
Purchase #5	$22.67	10.348%	$25.0159	$25.02	$25.00	$25.00
Purchase #6	$30.53	5.253%	$32.1337	$32.13	$32.15	$32.10
Purchase #7	$180.25	5.566%	$190.2827	$190.28	$190.30	$190.30
7 purchase totals =	$581.61		$635.8167	$635.82	$635.80	$635.90