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	$165.80	11.850%	$185.4473	$185.45	$185.45	$185.40
Purchase #2	$201.42	6.499%	$214.5103	$214.51	$214.50	$214.50
Purchase #3	$60.95	3.630%	$63.1625	$63.16	$63.15	$63.20
Purchase #4	$108.69	5.134%	$114.2701	$114.27	$114.25	$114.30
Purchase #5	$125.57	4.661%	$131.4228	$131.42	$131.40	$131.40
Purchase #6	$145.38	12.855%	$164.0686	$164.07	$164.05	$164.10
Purchase #7	$60.71	3.430%	$62.7924	$62.79	$62.80	$62.80
7 purchase totals =	$868.52		$935.6740	$935.67	$935.60	$935.70