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	$43.88	5.847%	$46.4457	$46.45	$46.45	$46.40
Purchase #2	$104.83	8.147%	$113.3705	$113.37	$113.35	$113.40
Purchase #3	$117.73	3.436%	$121.7752	$121.78	$121.80	$121.80
Purchase #4	$83.56	7.135%	$89.522	$89.52	$89.50	$89.50
Purchase #5	$42.44	10.215%	$46.7752	$46.78	$46.80	$46.80
Purchase #6	$217.94	10.760%	$241.3903	$241.39	$241.40	$241.40
Purchase #7	$78.66	9.182%	$85.8826	$85.88	$85.90	$85.90
7 purchase totals =	$689.04		$745.1615	$745.17	$745.20	$745.20