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	$120.72	5.712%	$127.6155	$127.62	$127.60	$127.60
Purchase #2	$75.33	7.423%	$80.9217	$80.92	$80.90	$80.90
Purchase #3	$187.37	9.256%	$204.713	$204.71	$204.70	$204.70
Purchase #4	$123.99	8.590%	$134.6407	$134.64	$134.65	$134.60
Purchase #5	$41.30	8.335%	$44.7424	$44.74	$44.75	$44.70
Purchase #6	$158.53	6.533%	$168.8868	$168.89	$168.90	$168.90
Purchase #7	$240.47	7.417%	$258.3057	$258.31	$258.30	$258.30
7 purchase totals =	$947.71		$1,019.8258	$1,019.83	$1,019.80	$1,019.70