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	$66.96	8.825%	$72.8692	$72.87	$72.85	$72.90
Purchase #2	$15.61	3.797%	$16.2027	$16.20	$16.20	$16.20
Purchase #3	$183.50	7.197%	$196.7065	$196.71	$196.70	$196.70
Purchase #4	$98.94	4.845%	$103.7336	$103.73	$103.75	$103.70
Purchase #5	$128.72	10.247%	$141.9099	$141.91	$141.90	$141.90
Purchase #6	$23.40	10.711%	$25.9064	$25.91	$25.90	$25.90
Purchase #7	$62.26	8.719%	$67.6884	$67.69	$67.70	$67.70
7 purchase totals =	$579.39		$625.0167	$625.02	$625.00	$625.00