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	$102.86	9.504%	$112.6358	$112.64	$112.65	$112.60
Purchase #2	$49.83	6.712%	$53.1746	$53.17	$53.15	$53.20
Purchase #3	$158.48	13.346%	$179.6307	$179.63	$179.65	$179.60
Purchase #4	$137.89	3.461%	$142.6624	$142.66	$142.65	$142.70
Purchase #5	$147.67	4.485%	$154.293	$154.29	$154.30	$154.30
Purchase #6	$250.71	5.676%	$264.9403	$264.94	$264.95	$264.90
Purchase #7	$54.67	8.838%	$59.5017	$59.50	$59.50	$59.50
7 purchase totals =	$902.11		$966.8385	$966.83	$966.85	$966.80