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	$81.56	4.797%	$85.4724	$85.47	$85.45	$85.50
Purchase #2	$111.61	6.464%	$118.8245	$118.82	$118.80	$118.80
Purchase #3	$168.75	7.689%	$181.7252	$181.73	$181.75	$181.70
Purchase #4	$197.43	8.664%	$214.5353	$214.54	$214.55	$214.50
Purchase #5	$167.63	4.439%	$175.0711	$175.07	$175.05	$175.10
Purchase #6	$105.71	11.402%	$117.7631	$117.76	$117.75	$117.80
Purchase #7	$145.56	3.741%	$151.0054	$151.01	$151.00	$151.00
7 purchase totals =	$978.25		$1,044.3970	$1,044.40	$1,044.35	$1,044.40