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	$59.32	11.805%	$66.3227	$66.32	$66.30	$66.30
Purchase #2	$93.36	13.481%	$105.9459	$105.95	$105.95	$105.90
Purchase #3	$5.71	3.389%	$5.9035	$5.90	$5.90	$5.90
Purchase #4	$151.93	6.237%	$161.4059	$161.41	$161.40	$161.40
Purchase #5	$245.57	11.306%	$273.3341	$273.33	$273.35	$273.30
Purchase #6	$157.54	6.303%	$167.4697	$167.47	$167.45	$167.50
Purchase #7	$117.38	8.216%	$127.0239	$127.02	$127.00	$127.00
7 purchase totals =	$830.81		$907.4057	$907.40	$907.35	$907.30