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	$43.28	3.639%	$44.855	$44.86	$44.85	$44.90
Purchase #2	$226.44	3.264%	$233.831	$233.83	$233.85	$233.80
Purchase #3	$66.67	12.154%	$74.7731	$74.77	$74.75	$74.80
Purchase #4	$96.46	5.308%	$101.5801	$101.58	$101.60	$101.60
Purchase #5	$146.97	12.221%	$164.9312	$164.93	$164.95	$164.90
Purchase #6	$185.98	5.674%	$196.5325	$196.53	$196.55	$196.50
Purchase #7	$27.25	11.449%	$30.3699	$30.37	$30.35	$30.40
7 purchase totals =	$793.05		$846.8728	$846.87	$846.90	$846.90