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	$99.85	13.267%	$113.0971	$113.10	$113.10	$113.10
Purchase #2	$162.63	11.225%	$180.8852	$180.89	$180.90	$180.90
Purchase #3	$239.68	8.493%	$260.036	$260.04	$260.05	$260.00
Purchase #4	$143.46	11.624%	$160.1358	$160.14	$160.15	$160.10
Purchase #5	$95.53	9.352%	$104.464	$104.46	$104.45	$104.50
Purchase #6	$105.72	7.258%	$113.3932	$113.39	$113.40	$113.40
Purchase #7	$30.69	5.272%	$32.308	$32.31	$32.30	$32.30
7 purchase totals =	$877.56		$964.3193	$964.33	$964.35	$964.30