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	$63.36	6.673%	$67.588	$67.59	$67.60	$67.60
Purchase #2	$228.94	3.262%	$236.408	$236.41	$236.40	$236.40
Purchase #3	$179.63	13.106%	$203.1723	$203.17	$203.15	$203.20
Purchase #4	$50.27	13.433%	$57.0228	$57.02	$57.00	$57.00
Purchase #5	$52.25	4.504%	$54.6033	$54.60	$54.60	$54.60
Purchase #6	$206.82	5.487%	$218.1682	$218.17	$218.15	$218.20
Purchase #7	$159.36	13.492%	$180.8609	$180.86	$180.85	$180.90
7 purchase totals =	$940.63		$1,017.8235	$1,017.82	$1,017.75	$1,017.90