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	$23.87	8.568%	$25.9152	$25.92	$25.90	$25.90
Purchase #2	$82.64	7.764%	$89.0562	$89.06	$89.05	$89.10
Purchase #3	$250.25	4.527%	$261.5788	$261.58	$261.60	$261.60
Purchase #4	$150.66	9.340%	$164.7316	$164.73	$164.75	$164.70
Purchase #5	$170.84	4.459%	$178.4578	$178.46	$178.45	$178.50
Purchase #6	$106.80	4.318%	$111.4116	$111.41	$111.40	$111.40
Purchase #7	$177.82	10.673%	$196.7987	$196.80	$196.80	$196.80
7 purchase totals =	$962.88		$1,027.9499	$1,027.96	$1,027.95	$1,028.00