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	$138.81	10.860%	$153.8848	$153.88	$153.90	$153.90
Purchase #2	$117.56	8.675%	$127.7583	$127.76	$127.75	$127.80
Purchase #3	$68.60	3.435%	$70.9564	$70.96	$70.95	$71.00
Purchase #4	$174.56	4.631%	$182.6439	$182.64	$182.65	$182.60
Purchase #5	$158.60	3.553%	$164.2351	$164.24	$164.25	$164.20
Purchase #6	$48.59	11.498%	$54.1769	$54.18	$54.20	$54.20
Purchase #7	$188.93	12.276%	$212.123	$212.12	$212.10	$212.10
7 purchase totals =	$895.65		$965.7784	$965.78	$965.80	$965.80