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	$175.89	11.181%	$195.5563	$195.56	$195.55	$195.60
Purchase #2	$125.38	5.113%	$131.7907	$131.79	$131.80	$131.80
Purchase #3	$43.53	11.824%	$48.677	$48.68	$48.70	$48.70
Purchase #4	$134.80	6.774%	$143.9314	$143.93	$143.95	$143.90
Purchase #5	$127.78	13.365%	$144.8578	$144.86	$144.85	$144.90
Purchase #6	$71.43	7.589%	$76.8508	$76.85	$76.85	$76.90
Purchase #7	$43.66	11.686%	$48.7621	$48.76	$48.75	$48.80
7 purchase totals =	$722.47		$790.4261	$790.43	$790.45	$790.60