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	$14.46	6.795%	$15.4426	$15.44	$15.45	$15.40
Purchase #2	$210.33	6.750%	$224.5273	$224.53	$224.55	$224.50
Purchase #3	$20.30	4.275%	$21.1678	$21.17	$21.15	$21.20
Purchase #4	$191.89	4.536%	$200.5941	$200.59	$200.60	$200.60
Purchase #5	$89.45	12.726%	$100.8334	$100.83	$100.85	$100.80
Purchase #6	$238.52	12.380%	$268.0488	$268.05	$268.05	$268.00
Purchase #7	$160.48	11.832%	$179.468	$179.47	$179.45	$179.50
7 purchase totals =	$925.43		$1,010.0820	$1,010.08	$1,010.10	$1,010.00