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	$126.33	11.605%	$140.9906	$140.99	$141.00	$141.00
Purchase #2	$56.67	13.676%	$64.4202	$64.42	$64.40	$64.40
Purchase #3	$143.27	9.824%	$157.3448	$157.34	$157.35	$157.30
Purchase #4	$174.42	5.261%	$183.5962	$183.60	$183.60	$183.60
Purchase #5	$154.40	12.640%	$173.9162	$173.92	$173.90	$173.90
Purchase #6	$141.69	7.545%	$152.3805	$152.38	$152.40	$152.40
Purchase #7	$184.54	6.697%	$196.8986	$196.90	$196.90	$196.90
7 purchase totals =	$981.32		$1,069.5471	$1,069.55	$1,069.55	$1,069.50