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	$240.34	11.495%	$267.9671	$267.97	$267.95	$268.00
Purchase #2	$113.98	3.592%	$118.0742	$118.07	$118.05	$118.10
Purchase #3	$69.42	4.565%	$72.589	$72.59	$72.60	$72.60
Purchase #4	$93.41	6.627%	$99.6003	$99.60	$99.60	$99.60
Purchase #5	$35.38	13.829%	$40.2727	$40.27	$40.25	$40.30
Purchase #6	$222.71	11.134%	$247.5065	$247.51	$247.50	$247.50
Purchase #7	$223.60	5.720%	$236.3899	$236.39	$236.40	$236.40
7 purchase totals =	$998.84		$1,082.3997	$1,082.40	$1,082.35	$1,082.50