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	$231.61	10.432%	$255.7716	$255.77	$255.75	$255.80
Purchase #2	$87.69	3.348%	$90.6259	$90.63	$90.65	$90.60
Purchase #3	$12.47	7.149%	$13.3615	$13.36	$13.35	$13.40
Purchase #4	$164.35	3.287%	$169.7522	$169.75	$169.75	$169.80
Purchase #5	$36.37	12.434%	$40.8922	$40.89	$40.90	$40.90
Purchase #6	$173.44	3.361%	$179.2693	$179.27	$179.25	$179.30
Purchase #7	$158.93	9.726%	$174.3875	$174.39	$174.40	$174.40
7 purchase totals =	$864.86		$924.0602	$924.06	$924.05	$924.20