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	$51.82	4.369%	$54.084	$54.08	$54.10	$54.10
Purchase #2	$235.33	8.648%	$255.6813	$255.68	$255.70	$255.70
Purchase #3	$83.56	3.859%	$86.7846	$86.78	$86.80	$86.80
Purchase #4	$37.37	4.577%	$39.0804	$39.08	$39.10	$39.10
Purchase #5	$43.41	10.829%	$48.1109	$48.11	$48.10	$48.10
Purchase #6	$136.71	12.261%	$153.472	$153.47	$153.45	$153.50
Purchase #7	$222.35	3.363%	$229.8276	$229.83	$229.85	$229.80
7 purchase totals =	$810.55		$867.0408	$867.03	$867.10	$867.10