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	$80.52	7.378%	$86.4608	$86.46	$86.45	$86.50
Purchase #2	$121.92	7.742%	$131.359	$131.36	$131.35	$131.40
Purchase #3	$197.78	5.549%	$208.7548	$208.75	$208.75	$208.80
Purchase #4	$111.67	9.815%	$122.6304	$122.63	$122.65	$122.60
Purchase #5	$145.82	4.689%	$152.6575	$152.66	$152.65	$152.70
Purchase #6	$114.30	11.654%	$127.6205	$127.62	$127.60	$127.60
Purchase #7	$229.31	4.586%	$239.8262	$239.83	$239.85	$239.80
7 purchase totals =	$1,001.32		$1,069.3092	$1,069.31	$1,069.30	$1,069.40