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	$136.64	3.865%	$141.9211	$141.92	$141.90	$141.90
Purchase #2	$137.41	6.779%	$146.725	$146.73	$146.75	$146.70
Purchase #3	$151.66	9.824%	$166.5591	$166.56	$166.55	$166.60
Purchase #4	$168.95	3.798%	$175.3667	$175.37	$175.35	$175.40
Purchase #5	$69.56	4.241%	$72.51	$72.51	$72.50	$72.50
Purchase #6	$9.97	3.271%	$10.2961	$10.30	$10.30	$10.30
Purchase #7	$138.44	6.609%	$147.5895	$147.59	$147.60	$147.60
7 purchase totals =	$812.63		$860.9675	$860.98	$860.95	$861.00