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	$108.26	4.545%	$113.1804	$113.18	$113.20	$113.20
Purchase #2	$78.95	13.194%	$89.3667	$89.37	$89.35	$89.40
Purchase #3	$5.60	13.451%	$6.3533	$6.35	$6.35	$6.40
Purchase #4	$25.63	9.761%	$28.1317	$28.13	$28.15	$28.10
Purchase #5	$82.98	9.345%	$90.7345	$90.73	$90.75	$90.70
Purchase #6	$10.59	13.486%	$12.0182	$12.02	$12.00	$12.00
Purchase #7	$248.44	6.589%	$264.8097	$264.81	$264.80	$264.80
7 purchase totals =	$560.45		$604.5945	$604.59	$604.60	$604.60