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	$28.54	11.195%	$31.7351	$31.74	$31.75	$31.70
Purchase #2	$148.96	12.271%	$167.2389	$167.24	$167.25	$167.20
Purchase #3	$241.43	6.286%	$256.6063	$256.61	$256.60	$256.60
Purchase #4	$70.78	13.326%	$80.2121	$80.21	$80.20	$80.20
Purchase #5	$234.44	10.862%	$259.9049	$259.90	$259.90	$259.90
Purchase #6	$151.51	6.222%	$160.937	$160.94	$160.95	$160.90
Purchase #7	$50.63	8.518%	$54.9427	$54.94	$54.95	$54.90
7 purchase totals =	$926.29		$1,011.5770	$1,011.58	$1,011.60	$1,011.40