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	$61.26	10.835%	$67.8975	$67.90	$67.90	$67.90
Purchase #2	$37.57	13.280%	$42.5593	$42.56	$42.55	$42.60
Purchase #3	$198.50	10.235%	$218.8165	$218.82	$218.80	$218.80
Purchase #4	$38.39	12.333%	$43.1246	$43.12	$43.10	$43.10
Purchase #5	$9.93	5.848%	$10.5107	$10.51	$10.50	$10.50
Purchase #6	$113.95	4.566%	$119.153	$119.15	$119.15	$119.20
Purchase #7	$232.29	10.697%	$257.1381	$257.14	$257.15	$257.10
7 purchase totals =	$691.89		$759.1997	$759.20	$759.15	$759.20