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	$144.41	10.148%	$159.0647	$159.06	$159.05	$159.10
Purchase #2	$206.70	5.126%	$217.2954	$217.30	$217.30	$217.30
Purchase #3	$130.26	11.681%	$145.4757	$145.48	$145.50	$145.50
Purchase #4	$159.40	3.176%	$164.4625	$164.46	$164.45	$164.50
Purchase #5	$42.32	7.716%	$45.5854	$45.59	$45.60	$45.60
Purchase #6	$146.31	11.372%	$162.9484	$162.95	$162.95	$162.90
Purchase #7	$218.64	9.290%	$238.9517	$238.95	$238.95	$239.00
7 purchase totals =	$1,048.04		$1,133.7838	$1,133.79	$1,133.80	$1,133.90