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	$172.64	11.594%	$192.6559	$192.66	$192.65	$192.70
Purchase #2	$64.35	4.709%	$67.3802	$67.38	$67.40	$67.40
Purchase #3	$196.57	7.802%	$211.9064	$211.91	$211.90	$211.90
Purchase #4	$161.90	5.706%	$171.138	$171.14	$171.15	$171.10
Purchase #5	$135.40	11.208%	$150.5756	$150.58	$150.60	$150.60
Purchase #6	$5.52	3.665%	$5.7223	$5.72	$5.70	$5.70
Purchase #7	$24.64	11.189%	$27.397	$27.40	$27.40	$27.40
7 purchase totals =	$761.02		$826.7754	$826.79	$826.80	$826.80