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	$72.97	13.349%	$82.7108	$82.71	$82.70	$82.70
Purchase #2	$172.80	13.621%	$196.3371	$196.34	$196.35	$196.30
Purchase #3	$156.37	6.555%	$166.6201	$166.62	$166.60	$166.60
Purchase #4	$224.64	12.594%	$252.9312	$252.93	$252.95	$252.90
Purchase #5	$57.81	3.612%	$59.8981	$59.90	$59.90	$59.90
Purchase #6	$195.75	3.857%	$203.3001	$203.30	$203.30	$203.30
Purchase #7	$7.72	13.738%	$8.7806	$8.78	$8.80	$8.80
7 purchase totals =	$888.06		$970.5780	$970.58	$970.60	$970.50