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	$134.33	11.870%	$150.275	$150.28	$150.30	$150.30
Purchase #2	$16.38	11.544%	$18.2709	$18.27	$18.25	$18.30
Purchase #3	$40.59	12.850%	$45.8058	$45.81	$45.80	$45.80
Purchase #4	$182.93	12.155%	$205.1651	$205.17	$205.15	$205.20
Purchase #5	$99.93	11.287%	$111.2091	$111.21	$111.20	$111.20
Purchase #6	$65.60	9.149%	$71.6017	$71.60	$71.60	$71.60
Purchase #7	$177.70	12.578%	$200.0511	$200.05	$200.05	$200.10
7 purchase totals =	$717.46		$802.3787	$802.39	$802.35	$802.50