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	$159.57	11.185%	$177.4179	$177.42	$177.40	$177.40
Purchase #2	$240.83	5.495%	$254.0636	$254.06	$254.05	$254.10
Purchase #3	$67.30	6.824%	$71.8926	$71.89	$71.90	$71.90
Purchase #4	$216.46	4.224%	$225.6033	$225.60	$225.60	$225.60
Purchase #5	$89.38	5.648%	$94.4282	$94.43	$94.45	$94.40
Purchase #6	$155.29	10.693%	$171.8952	$171.90	$171.90	$171.90
Purchase #7	$10.29	4.225%	$10.7248	$10.72	$10.70	$10.70
7 purchase totals =	$939.12		$1,006.0256	$1,006.02	$1,006.00	$1,006.00