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	$157.71	13.486%	$178.9788	$178.98	$179.00	$179.00
Purchase #2	$98.62	6.405%	$104.9366	$104.94	$104.95	$104.90
Purchase #3	$41.72	4.232%	$43.4856	$43.49	$43.50	$43.50
Purchase #4	$232.40	13.236%	$263.1605	$263.16	$263.15	$263.20
Purchase #5	$121.33	7.833%	$130.8338	$130.83	$130.85	$130.80
Purchase #6	$150.25	5.213%	$158.0825	$158.08	$158.10	$158.10
Purchase #7	$117.84	12.438%	$132.4969	$132.50	$132.50	$132.50
7 purchase totals =	$919.87		$1,011.9747	$1,011.98	$1,012.05	$1,012.00