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	$33.33	3.159%	$34.3829	$34.38	$34.40	$34.40
Purchase #2	$96.45	7.569%	$103.7503	$103.75	$103.75	$103.80
Purchase #3	$100.98	7.477%	$108.5303	$108.53	$108.55	$108.50
Purchase #4	$79.54	4.639%	$83.2299	$83.23	$83.25	$83.20
Purchase #5	$147.93	13.468%	$167.8532	$167.85	$167.85	$167.90
Purchase #6	$68.73	13.786%	$78.2051	$78.21	$78.20	$78.20
Purchase #7	$153.68	10.382%	$169.6351	$169.64	$169.65	$169.60
7 purchase totals =	$680.64		$745.5868	$745.59	$745.65	$745.60