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	$114.71	4.173%	$119.4968	$119.50	$119.50	$119.50
Purchase #2	$23.68	5.487%	$24.9793	$24.98	$25.00	$25.00
Purchase #3	$81.99	10.457%	$90.5637	$90.56	$90.55	$90.60
Purchase #4	$16.54	9.272%	$18.0736	$18.07	$18.05	$18.10
Purchase #5	$202.80	11.210%	$225.5339	$225.53	$225.55	$225.50
Purchase #6	$200.62	11.153%	$222.9951	$223.00	$223.00	$223.00
Purchase #7	$52.48	13.799%	$59.7217	$59.72	$59.70	$59.70
7 purchase totals =	$692.82		$761.3641	$761.36	$761.35	$761.40