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	$225.50	5.558%	$238.0333	$238.03	$238.05	$238.00
Purchase #2	$193.54	11.855%	$216.4842	$216.48	$216.50	$216.50
Purchase #3	$159.33	5.170%	$167.5674	$167.57	$167.55	$167.60
Purchase #4	$150.98	3.189%	$155.7948	$155.79	$155.80	$155.80
Purchase #5	$217.82	6.212%	$231.351	$231.35	$231.35	$231.40
Purchase #6	$121.29	5.192%	$127.5874	$127.59	$127.60	$127.60
Purchase #7	$59.81	5.434%	$63.0601	$63.06	$63.05	$63.10
7 purchase totals =	$1,128.27		$1,199.8782	$1,199.87	$1,199.90	$1,200.00