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	$233.34	9.631%	$255.813	$255.81	$255.80	$255.80
Purchase #2	$78.80	9.741%	$86.4759	$86.48	$86.50	$86.50
Purchase #3	$244.49	5.444%	$257.8	$257.80	$257.80	$257.80
Purchase #4	$43.40	4.298%	$45.2653	$45.27	$45.25	$45.30
Purchase #5	$164.71	9.838%	$180.9142	$180.91	$180.90	$180.90
Purchase #6	$120.39	7.589%	$129.5264	$129.53	$129.55	$129.50
Purchase #7	$71.76	12.209%	$80.5212	$80.52	$80.50	$80.50
7 purchase totals =	$956.89		$1,036.3160	$1,036.32	$1,036.30	$1,036.30