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	$76.72	5.492%	$80.9335	$80.93	$80.95	$80.90
Purchase #2	$155.98	6.658%	$166.3651	$166.37	$166.35	$166.40
Purchase #3	$34.78	12.156%	$39.0079	$39.01	$39.00	$39.00
Purchase #4	$31.58	4.345%	$32.9522	$32.95	$32.95	$33.00
Purchase #5	$218.79	6.569%	$233.1623	$233.16	$233.15	$233.20
Purchase #6	$167.35	7.314%	$179.59	$179.59	$179.60	$179.60
Purchase #7	$127.52	3.271%	$131.6912	$131.69	$131.70	$131.70
7 purchase totals =	$812.72		$863.7022	$863.70	$863.70	$863.80