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	$66.44	10.675%	$73.5325	$73.53	$73.55	$73.50
Purchase #2	$150.39	11.224%	$167.2698	$167.27	$167.25	$167.30
Purchase #3	$35.32	5.377%	$37.2192	$37.22	$37.20	$37.20
Purchase #4	$130.60	11.118%	$145.1201	$145.12	$145.10	$145.10
Purchase #5	$162.40	12.807%	$183.1986	$183.20	$183.20	$183.20
Purchase #6	$149.44	10.528%	$165.173	$165.17	$165.15	$165.20
Purchase #7	$158.51	9.589%	$173.7095	$173.71	$173.70	$173.70
7 purchase totals =	$853.10		$945.2227	$945.22	$945.15	$945.20