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	$159.53	8.672%	$173.3644	$173.36	$173.35	$173.40
Purchase #2	$34.28	10.220%	$37.7834	$37.78	$37.80	$37.80
Purchase #3	$217.25	4.857%	$227.8018	$227.80	$227.80	$227.80
Purchase #4	$10.42	9.798%	$11.441	$11.44	$11.45	$11.40
Purchase #5	$37.30	9.524%	$40.8525	$40.85	$40.85	$40.90
Purchase #6	$51.26	6.607%	$54.6467	$54.65	$54.65	$54.60
Purchase #7	$206.55	8.197%	$223.4809	$223.48	$223.50	$223.50
7 purchase totals =	$716.59		$769.3707	$769.36	$769.40	$769.40