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	$72.98	9.810%	$80.1393	$80.14	$80.15	$80.10
Purchase #2	$53.78	9.231%	$58.7444	$58.74	$58.75	$58.70
Purchase #3	$64.91	3.219%	$66.9995	$67.00	$67.00	$67.00
Purchase #4	$152.27	13.558%	$172.9148	$172.91	$172.90	$172.90
Purchase #5	$26.77	5.470%	$28.2343	$28.23	$28.25	$28.20
Purchase #6	$132.32	7.704%	$142.5139	$142.51	$142.50	$142.50
Purchase #7	$13.26	10.823%	$14.6951	$14.70	$14.70	$14.70
7 purchase totals =	$516.29		$564.2413	$564.23	$564.25	$564.10