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	$144.91	12.635%	$163.2194	$163.22	$163.20	$163.20
Purchase #2	$86.44	3.482%	$89.4498	$89.45	$89.45	$89.40
Purchase #3	$16.93	9.409%	$18.5229	$18.52	$18.50	$18.50
Purchase #4	$18.96	3.275%	$19.5809	$19.58	$19.60	$19.60
Purchase #5	$119.56	7.815%	$128.9036	$128.90	$128.90	$128.90
Purchase #6	$200.77	5.369%	$211.5493	$211.55	$211.55	$211.50
Purchase #7	$39.80	13.471%	$45.1615	$45.16	$45.15	$45.20
7 purchase totals =	$627.37		$676.3874	$676.38	$676.35	$676.30