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	$200.96	7.644%	$216.3214	$216.32	$216.30	$216.30
Purchase #2	$162.53	13.493%	$184.4602	$184.46	$184.45	$184.50
Purchase #3	$24.85	13.196%	$28.1292	$28.13	$28.15	$28.10
Purchase #4	$127.53	11.247%	$141.8733	$141.87	$141.85	$141.90
Purchase #5	$183.57	12.459%	$206.441	$206.44	$206.45	$206.40
Purchase #6	$167.95	11.385%	$187.0711	$187.07	$187.05	$187.10
Purchase #7	$164.51	9.697%	$180.4625	$180.46	$180.45	$180.50
7 purchase totals =	$1,031.90		$1,144.7587	$1,144.75	$1,144.70	$1,144.80