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	$184.78	12.795%	$208.4226	$208.42	$208.40	$208.40
Purchase #2	$196.71	12.479%	$221.2574	$221.26	$221.25	$221.30
Purchase #3	$86.96	3.647%	$90.1314	$90.13	$90.15	$90.10
Purchase #4	$191.87	7.868%	$206.9663	$206.97	$206.95	$207.00
Purchase #5	$98.53	4.634%	$103.0959	$103.10	$103.10	$103.10
Purchase #6	$135.59	10.333%	$149.6005	$149.60	$149.60	$149.60
Purchase #7	$99.48	7.176%	$106.6187	$106.62	$106.60	$106.60
7 purchase totals =	$993.92		$1,086.0928	$1,086.10	$1,086.05	$1,086.10