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	$176.87	3.167%	$182.4715	$182.47	$182.45	$182.50
Purchase #2	$38.87	8.115%	$42.0243	$42.02	$42.00	$42.00
Purchase #3	$187.53	4.777%	$196.4883	$196.49	$196.50	$196.50
Purchase #4	$210.48	13.344%	$238.5665	$238.57	$238.55	$238.60
Purchase #5	$159.48	13.344%	$180.761	$180.76	$180.75	$180.80
Purchase #6	$10.87	11.676%	$12.1392	$12.14	$12.15	$12.10
Purchase #7	$147.97	4.616%	$154.8003	$154.80	$154.80	$154.80
7 purchase totals =	$932.07		$1,007.2511	$1,007.25	$1,007.20	$1,007.30