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	$179.46	9.115%	$195.8178	$195.82	$195.80	$195.80
Purchase #2	$249.77	11.426%	$278.3087	$278.31	$278.30	$278.30
Purchase #3	$49.34	3.793%	$51.2115	$51.21	$51.20	$51.20
Purchase #4	$106.94	10.724%	$118.4082	$118.41	$118.40	$118.40
Purchase #5	$68.60	4.216%	$71.4922	$71.49	$71.50	$71.50
Purchase #6	$233.40	7.185%	$250.1698	$250.17	$250.15	$250.20
Purchase #7	$164.39	10.177%	$181.12	$181.12	$181.10	$181.10
7 purchase totals =	$1,051.90		$1,146.5282	$1,146.53	$1,146.45	$1,146.50