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	$171.47	9.388%	$187.5676	$187.57	$187.55	$187.60
Purchase #2	$166.27	7.795%	$179.2307	$179.23	$179.25	$179.20
Purchase #3	$207.75	8.172%	$224.7273	$224.73	$224.75	$224.70
Purchase #4	$70.33	11.217%	$78.2189	$78.22	$78.20	$78.20
Purchase #5	$11.34	10.388%	$12.518	$12.52	$12.50	$12.50
Purchase #6	$49.76	3.632%	$51.5673	$51.57	$51.55	$51.60
Purchase #7	$161.94	3.397%	$167.4411	$167.44	$167.45	$167.40
7 purchase totals =	$838.86		$901.2709	$901.28	$901.25	$901.20