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	$67.63	6.868%	$72.2748	$72.27	$72.25	$72.30
Purchase #2	$75.63	3.309%	$78.1326	$78.13	$78.15	$78.10
Purchase #3	$172.41	3.146%	$177.834	$177.83	$177.85	$177.80
Purchase #4	$36.41	11.640%	$40.6481	$40.65	$40.65	$40.60
Purchase #5	$21.86	8.599%	$23.7397	$23.74	$23.75	$23.70
Purchase #6	$184.92	8.358%	$200.3756	$200.38	$200.40	$200.40
Purchase #7	$151.64	10.371%	$167.3666	$167.37	$167.35	$167.40
7 purchase totals =	$710.50		$760.3714	$760.37	$760.40	$760.30