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	$71.95	9.332%	$78.6644	$78.66	$78.65	$78.70
Purchase #2	$240.48	3.776%	$249.5605	$249.56	$249.55	$249.60
Purchase #3	$23.26	10.482%	$25.6981	$25.70	$25.70	$25.70
Purchase #4	$147.25	13.541%	$167.1891	$167.19	$167.20	$167.20
Purchase #5	$162.68	10.585%	$179.8997	$179.90	$179.90	$179.90
Purchase #6	$80.78	11.149%	$89.7862	$89.79	$89.80	$89.80
Purchase #7	$139.44	9.564%	$152.776	$152.78	$152.80	$152.80
7 purchase totals =	$865.84		$943.5740	$943.58	$943.60	$943.70