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	$167.30	3.189%	$172.6352	$172.64	$172.65	$172.60
Purchase #2	$94.38	10.844%	$104.6146	$104.61	$104.60	$104.60
Purchase #3	$63.55	12.770%	$71.6653	$71.67	$71.65	$71.70
Purchase #4	$88.54	4.665%	$92.6704	$92.67	$92.65	$92.70
Purchase #5	$57.72	12.495%	$64.9321	$64.93	$64.95	$64.90
Purchase #6	$234.76	5.516%	$247.7094	$247.71	$247.70	$247.70
Purchase #7	$32.93	4.192%	$34.3104	$34.31	$34.30	$34.30
7 purchase totals =	$739.18		$788.5374	$788.54	$788.50	$788.50