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	$194.63	4.665%	$203.7095	$203.71	$203.70	$203.70
Purchase #2	$76.89	10.807%	$85.1995	$85.20	$85.20	$85.20
Purchase #3	$161.42	10.752%	$178.7759	$178.78	$178.80	$178.80
Purchase #4	$113.45	8.618%	$123.2271	$123.23	$123.25	$123.20
Purchase #5	$21.40	9.294%	$23.3889	$23.39	$23.40	$23.40
Purchase #6	$184.88	3.481%	$191.3157	$191.32	$191.30	$191.30
Purchase #7	$191.76	4.422%	$200.2396	$200.24	$200.25	$200.20
7 purchase totals =	$944.43		$1,005.8562	$1,005.87	$1,005.90	$1,005.80