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	$127.75	3.223%	$131.8674	$131.87	$131.85	$131.90
Purchase #2	$56.63	12.849%	$63.9064	$63.91	$63.90	$63.90
Purchase #3	$212.25	13.694%	$241.3155	$241.32	$241.30	$241.30
Purchase #4	$26.34	7.418%	$28.2939	$28.29	$28.30	$28.30
Purchase #5	$130.96	8.594%	$142.2147	$142.21	$142.20	$142.20
Purchase #6	$125.77	4.429%	$131.3404	$131.34	$131.35	$131.30
Purchase #7	$159.82	10.333%	$176.3342	$176.33	$176.35	$176.30
7 purchase totals =	$839.52		$915.2725	$915.27	$915.25	$915.20