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	$145.89	9.427%	$159.6431	$159.64	$159.65	$159.60
Purchase #2	$175.53	6.469%	$186.885	$186.89	$186.90	$186.90
Purchase #3	$136.76	10.129%	$150.6124	$150.61	$150.60	$150.60
Purchase #4	$118.51	3.870%	$123.0963	$123.10	$123.10	$123.10
Purchase #5	$30.77	13.436%	$34.9043	$34.90	$34.90	$34.90
Purchase #6	$94.59	11.153%	$105.1396	$105.14	$105.15	$105.10
Purchase #7	$178.91	3.150%	$184.5457	$184.55	$184.55	$184.50
7 purchase totals =	$880.96		$944.8264	$944.83	$944.85	$944.70