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	$155.64	4.676%	$162.9177	$162.92	$162.90	$162.90
Purchase #2	$235.66	5.758%	$249.2293	$249.23	$249.25	$249.20
Purchase #3	$164.85	4.459%	$172.2007	$172.20	$172.20	$172.20
Purchase #4	$78.95	10.748%	$87.4355	$87.44	$87.45	$87.40
Purchase #5	$118.31	11.490%	$131.9038	$131.90	$131.90	$131.90
Purchase #6	$84.91	4.295%	$88.5569	$88.56	$88.55	$88.60
Purchase #7	$177.40	7.416%	$190.556	$190.56	$190.55	$190.60
7 purchase totals =	$1,015.72		$1,082.7999	$1,082.81	$1,082.80	$1,082.80