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	$137.32	11.631%	$153.2917	$153.29	$153.30	$153.30
Purchase #2	$65.90	3.762%	$68.3792	$68.38	$68.40	$68.40
Purchase #3	$43.87	4.299%	$45.756	$45.76	$45.75	$45.80
Purchase #4	$237.66	12.486%	$267.3342	$267.33	$267.35	$267.30
Purchase #5	$43.85	5.351%	$46.1964	$46.20	$46.20	$46.20
Purchase #6	$69.89	3.406%	$72.2705	$72.27	$72.25	$72.30
Purchase #7	$249.84	6.576%	$266.2695	$266.27	$266.25	$266.30
7 purchase totals =	$848.33		$919.4975	$919.50	$919.50	$919.60