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	$175.51	13.619%	$199.4127	$199.41	$199.40	$199.40
Purchase #2	$64.64	7.724%	$69.6328	$69.63	$69.65	$69.60
Purchase #3	$139.29	4.548%	$145.6249	$145.62	$145.60	$145.60
Purchase #4	$145.44	11.553%	$162.2427	$162.24	$162.25	$162.20
Purchase #5	$205.80	13.661%	$233.9143	$233.91	$233.90	$233.90
Purchase #6	$62.85	13.258%	$71.1827	$71.18	$71.20	$71.20
Purchase #7	$57.90	9.243%	$63.2517	$63.25	$63.25	$63.30
7 purchase totals =	$851.43		$945.2618	$945.24	$945.25	$945.20