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	$71.82	7.697%	$77.348	$77.35	$77.35	$77.30
Purchase #2	$211.27	6.240%	$224.4532	$224.45	$224.45	$224.50
Purchase #3	$129.50	5.448%	$136.5552	$136.56	$136.55	$136.60
Purchase #4	$240.86	5.823%	$254.8853	$254.89	$254.90	$254.90
Purchase #5	$71.87	7.708%	$77.4097	$77.41	$77.40	$77.40
Purchase #6	$38.32	9.176%	$41.8362	$41.84	$41.85	$41.80
Purchase #7	$118.73	7.696%	$127.8675	$127.87	$127.85	$127.90
7 purchase totals =	$882.37		$940.3551	$940.37	$940.35	$940.40