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	$45.87	4.409%	$47.8924	$47.89	$47.90	$47.90
Purchase #2	$158.59	3.587%	$164.2786	$164.28	$164.30	$164.30
Purchase #3	$187.64	11.277%	$208.8002	$208.80	$208.80	$208.80
Purchase #4	$91.54	5.699%	$96.7569	$96.76	$96.75	$96.80
Purchase #5	$59.32	4.571%	$62.0315	$62.03	$62.05	$62.00
Purchase #6	$116.37	9.804%	$127.7789	$127.78	$127.80	$127.80
Purchase #7	$223.43	10.409%	$246.6868	$246.69	$246.70	$246.70
7 purchase totals =	$882.76		$954.2253	$954.23	$954.30	$954.30