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	$168.29	5.607%	$177.726	$177.73	$177.75	$177.70
Purchase #2	$169.47	7.692%	$182.5056	$182.51	$182.50	$182.50
Purchase #3	$96.81	13.571%	$109.9481	$109.95	$109.95	$109.90
Purchase #4	$31.39	6.454%	$33.4159	$33.42	$33.40	$33.40
Purchase #5	$89.83	12.389%	$100.959	$100.96	$100.95	$101.00
Purchase #6	$55.92	13.152%	$63.2746	$63.27	$63.25	$63.30
Purchase #7	$152.71	12.798%	$172.2538	$172.25	$172.25	$172.30
7 purchase totals =	$764.42		$840.0830	$840.09	$840.05	$840.10