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	$133.42	8.259%	$144.4392	$144.44	$144.45	$144.40
Purchase #2	$154.30	13.377%	$174.9407	$174.94	$174.95	$174.90
Purchase #3	$102.73	8.306%	$111.2628	$111.26	$111.25	$111.30
Purchase #4	$43.81	4.475%	$45.7705	$45.77	$45.75	$45.80
Purchase #5	$94.62	8.378%	$102.5473	$102.55	$102.55	$102.50
Purchase #6	$63.51	5.737%	$67.1536	$67.15	$67.15	$67.20
Purchase #7	$249.83	7.811%	$269.3442	$269.34	$269.35	$269.30
7 purchase totals =	$842.22		$915.4583	$915.45	$915.45	$915.40