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	$176.82	13.422%	$200.5528	$200.55	$200.55	$200.60
Purchase #2	$11.76	4.793%	$12.3237	$12.32	$12.30	$12.30
Purchase #3	$177.87	6.860%	$190.0719	$190.07	$190.05	$190.10
Purchase #4	$61.30	12.541%	$68.9876	$68.99	$69.00	$69.00
Purchase #5	$64.87	11.793%	$72.5201	$72.52	$72.50	$72.50
Purchase #6	$68.37	4.742%	$71.6121	$71.61	$71.60	$71.60
Purchase #7	$240.31	3.505%	$248.7329	$248.73	$248.75	$248.70
7 purchase totals =	$801.30		$864.8011	$864.79	$864.75	$864.80