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	$53.71	4.756%	$56.2644	$56.26	$56.25	$56.30
Purchase #2	$150.72	6.850%	$161.0443	$161.04	$161.05	$161.00
Purchase #3	$105.52	4.130%	$109.878	$109.88	$109.90	$109.90
Purchase #4	$56.73	6.720%	$60.5423	$60.54	$60.55	$60.50
Purchase #5	$92.66	4.535%	$96.8621	$96.86	$96.85	$96.90
Purchase #6	$191.44	12.632%	$215.6227	$215.62	$215.60	$215.60
Purchase #7	$250.50	5.720%	$264.8286	$264.83	$264.85	$264.80
7 purchase totals =	$901.28		$965.0424	$965.03	$965.05	$965.00