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	$173.61	13.420%	$196.9085	$196.91	$196.90	$196.90
Purchase #2	$130.95	13.369%	$148.4567	$148.46	$148.45	$148.50
Purchase #3	$112.97	3.466%	$116.8855	$116.89	$116.90	$116.90
Purchase #4	$12.32	12.248%	$13.829	$13.83	$13.85	$13.80
Purchase #5	$112.61	6.311%	$119.7168	$119.72	$119.70	$119.70
Purchase #6	$51.56	5.264%	$54.2741	$54.27	$54.25	$54.30
Purchase #7	$39.75	7.619%	$42.7786	$42.78	$42.80	$42.80
7 purchase totals =	$633.77		$692.8492	$692.86	$692.85	$692.90