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	$243.40	7.459%	$261.5552	$261.56	$261.55	$261.60
Purchase #2	$203.33	5.487%	$214.4867	$214.49	$214.50	$214.50
Purchase #3	$212.39	7.217%	$227.7182	$227.72	$227.70	$227.70
Purchase #4	$139.33	13.787%	$158.5394	$158.54	$158.55	$158.50
Purchase #5	$45.70	13.421%	$51.8334	$51.83	$51.85	$51.80
Purchase #6	$160.56	4.818%	$168.2958	$168.30	$168.30	$168.30
Purchase #7	$250.96	3.549%	$259.8666	$259.87	$259.85	$259.90
7 purchase totals =	$1,255.67		$1,342.2953	$1,342.31	$1,342.30	$1,342.30