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	$70.82	11.127%	$78.7001	$78.70	$78.70	$78.70
Purchase #2	$244.90	4.649%	$256.2854	$256.29	$256.30	$256.30
Purchase #3	$98.41	10.842%	$109.0796	$109.08	$109.10	$109.10
Purchase #4	$231.61	6.287%	$246.1713	$246.17	$246.15	$246.20
Purchase #5	$186.88	3.265%	$192.9816	$192.98	$193.00	$193.00
Purchase #6	$74.89	4.265%	$78.0841	$78.08	$78.10	$78.10
Purchase #7	$173.78	10.525%	$192.0703	$192.07	$192.05	$192.10
7 purchase totals =	$1,081.29		$1,153.3724	$1,153.37	$1,153.40	$1,153.50