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	$183.58	11.220%	$204.1777	$204.18	$204.20	$204.20
Purchase #2	$82.81	3.475%	$85.6876	$85.69	$85.70	$85.70
Purchase #3	$86.45	4.557%	$90.3895	$90.39	$90.40	$90.40
Purchase #4	$63.80	13.710%	$72.547	$72.55	$72.55	$72.50
Purchase #5	$47.96	13.244%	$54.3118	$54.31	$54.30	$54.30
Purchase #6	$147.66	8.332%	$159.963	$159.96	$159.95	$160.00
Purchase #7	$18.65	12.439%	$20.9699	$20.97	$20.95	$21.00
7 purchase totals =	$630.91		$688.0465	$688.05	$688.05	$688.10