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	$126.81	12.295%	$142.4013	$142.40	$142.40	$142.40
Purchase #2	$162.44	10.459%	$179.4296	$179.43	$179.45	$179.40
Purchase #3	$144.86	13.364%	$164.2191	$164.22	$164.20	$164.20
Purchase #4	$23.89	7.206%	$25.6115	$25.61	$25.60	$25.60
Purchase #5	$244.60	7.431%	$262.7762	$262.78	$262.80	$262.80
Purchase #6	$145.54	13.804%	$165.6303	$165.63	$165.65	$165.60
Purchase #7	$61.78	13.226%	$69.951	$69.95	$69.95	$70.00
7 purchase totals =	$909.92		$1,010.0190	$1,010.02	$1,010.05	$1,010.00