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	$133.29	4.851%	$139.7559	$139.76	$139.75	$139.80
Purchase #2	$169.56	5.712%	$179.2453	$179.25	$179.25	$179.20
Purchase #3	$192.31	13.727%	$218.7084	$218.71	$218.70	$218.70
Purchase #4	$160.35	12.591%	$180.5397	$180.54	$180.55	$180.50
Purchase #5	$196.57	13.662%	$223.4254	$223.43	$223.45	$223.40
Purchase #6	$138.53	11.455%	$154.3986	$154.40	$154.40	$154.40
Purchase #7	$121.62	3.670%	$126.0835	$126.08	$126.10	$126.10
7 purchase totals =	$1,112.23		$1,222.1568	$1,222.17	$1,222.20	$1,222.10