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	$143.25	7.372%	$153.8104	$153.81	$153.80	$153.80
Purchase #2	$110.30	12.170%	$123.7235	$123.72	$123.70	$123.70
Purchase #3	$60.55	12.730%	$68.258	$68.26	$68.25	$68.30
Purchase #4	$85.94	10.447%	$94.9182	$94.92	$94.90	$94.90
Purchase #5	$100.41	4.276%	$104.7035	$104.70	$104.70	$104.70
Purchase #6	$103.50	7.745%	$111.5161	$111.52	$111.50	$111.50
Purchase #7	$63.65	11.642%	$71.0601	$71.06	$71.05	$71.10
7 purchase totals =	$667.60		$727.9898	$727.99	$727.90	$728.00