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	$117.50	4.799%	$123.1388	$123.14	$123.15	$123.10
Purchase #2	$187.33	4.844%	$196.4043	$196.40	$196.40	$196.40
Purchase #3	$108.51	7.485%	$116.632	$116.63	$116.65	$116.60
Purchase #4	$26.38	12.647%	$29.7163	$29.72	$29.70	$29.70
Purchase #5	$97.37	11.858%	$108.9161	$108.92	$108.90	$108.90
Purchase #6	$147.92	11.508%	$164.9426	$164.94	$164.95	$164.90
Purchase #7	$65.55	4.271%	$68.3496	$68.35	$68.35	$68.30
7 purchase totals =	$750.56		$808.0997	$808.10	$808.10	$807.90