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	$13.41	3.624%	$13.896	$13.90	$13.90	$13.90
Purchase #2	$47.96	9.454%	$52.4941	$52.49	$52.50	$52.50
Purchase #3	$174.52	12.844%	$196.9353	$196.94	$196.95	$196.90
Purchase #4	$142.64	9.533%	$156.2379	$156.24	$156.25	$156.20
Purchase #5	$193.72	9.730%	$212.569	$212.57	$212.55	$212.60
Purchase #6	$98.79	10.797%	$109.4564	$109.46	$109.45	$109.50
Purchase #7	$52.67	3.315%	$54.416	$54.42	$54.40	$54.40
7 purchase totals =	$723.71		$796.0047	$796.02	$796.00	$796.00