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	$54.66	5.599%	$57.7204	$57.72	$57.70	$57.70
Purchase #2	$178.93	11.297%	$199.1437	$199.14	$199.15	$199.10
Purchase #3	$179.83	11.708%	$200.8845	$200.88	$200.90	$200.90
Purchase #4	$110.55	3.680%	$114.6182	$114.62	$114.60	$114.60
Purchase #5	$211.43	12.133%	$237.0828	$237.08	$237.10	$237.10
Purchase #6	$112.34	10.127%	$123.7167	$123.72	$123.70	$123.70
Purchase #7	$62.90	12.468%	$70.7424	$70.74	$70.75	$70.70
7 purchase totals =	$910.64		$1,003.9087	$1,003.90	$1,003.90	$1,003.80