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	$215.94	11.819%	$241.4619	$241.46	$241.45	$241.50
Purchase #2	$10.65	7.309%	$11.4284	$11.43	$11.45	$11.40
Purchase #3	$145.99	12.617%	$164.4096	$164.41	$164.40	$164.40
Purchase #4	$142.34	10.280%	$156.9726	$156.97	$156.95	$157.00
Purchase #5	$98.47	11.158%	$109.4573	$109.46	$109.45	$109.50
Purchase #6	$220.69	13.453%	$250.3794	$250.38	$250.40	$250.40
Purchase #7	$143.66	5.658%	$151.7883	$151.79	$151.80	$151.80
7 purchase totals =	$977.74		$1,085.8975	$1,085.90	$1,085.90	$1,086.00