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	$37.43	11.483%	$41.7281	$41.73	$41.75	$41.70
Purchase #2	$74.60	4.845%	$78.2144	$78.21	$78.20	$78.20
Purchase #3	$35.26	11.484%	$39.3093	$39.31	$39.30	$39.30
Purchase #4	$106.81	7.552%	$114.8763	$114.88	$114.90	$114.90
Purchase #5	$13.62	12.492%	$15.3214	$15.32	$15.30	$15.30
Purchase #6	$155.76	11.328%	$173.4045	$173.40	$173.40	$173.40
Purchase #7	$30.91	4.811%	$32.3971	$32.40	$32.40	$32.40
7 purchase totals =	$454.39		$495.2511	$495.25	$495.25	$495.20