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	$246.41	7.540%	$264.9893	$264.99	$265.00	$265.00
Purchase #2	$16.51	9.500%	$18.0785	$18.08	$18.10	$18.10
Purchase #3	$127.82	11.325%	$142.2956	$142.30	$142.30	$142.30
Purchase #4	$142.70	6.184%	$151.5246	$151.52	$151.50	$151.50
Purchase #5	$137.29	5.263%	$144.5156	$144.52	$144.50	$144.50
Purchase #6	$168.83	10.770%	$187.013	$187.01	$187.00	$187.00
Purchase #7	$211.52	11.314%	$235.4514	$235.45	$235.45	$235.50
7 purchase totals =	$1,051.08		$1,143.8680	$1,143.87	$1,143.85	$1,143.90