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	$44.40	13.442%	$50.3682	$50.37	$50.35	$50.40
Purchase #2	$69.92	12.129%	$78.4006	$78.40	$78.40	$78.40
Purchase #3	$245.56	3.369%	$253.8329	$253.83	$253.85	$253.80
Purchase #4	$175.30	6.595%	$186.861	$186.86	$186.85	$186.90
Purchase #5	$126.50	13.760%	$143.9064	$143.91	$143.90	$143.90
Purchase #6	$161.33	9.160%	$176.1078	$176.11	$176.10	$176.10
Purchase #7	$223.97	7.838%	$241.5248	$241.52	$241.50	$241.50
7 purchase totals =	$1,046.98		$1,131.0017	$1,131.00	$1,130.95	$1,131.00