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	$44.48	11.152%	$49.4404	$49.44	$49.45	$49.40
Purchase #2	$11.55	7.372%	$12.4015	$12.40	$12.40	$12.40
Purchase #3	$81.99	8.874%	$89.2658	$89.27	$89.25	$89.30
Purchase #4	$98.41	12.861%	$111.0665	$111.07	$111.05	$111.10
Purchase #5	$209.44	13.780%	$238.3008	$238.30	$238.30	$238.30
Purchase #6	$202.66	11.444%	$225.8524	$225.85	$225.85	$225.90
Purchase #7	$30.43	9.770%	$33.403	$33.40	$33.40	$33.40
7 purchase totals =	$678.96		$759.7304	$759.73	$759.70	$759.80