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	$23.96	5.261%	$25.2205	$25.22	$25.20	$25.20
Purchase #2	$87.58	6.740%	$93.4829	$93.48	$93.50	$93.50
Purchase #3	$248.61	10.462%	$274.6196	$274.62	$274.60	$274.60
Purchase #4	$137.51	5.799%	$145.4842	$145.48	$145.50	$145.50
Purchase #5	$181.42	5.608%	$191.594	$191.59	$191.60	$191.60
Purchase #6	$181.56	8.211%	$196.4679	$196.47	$196.45	$196.50
Purchase #7	$178.61	9.228%	$195.0921	$195.09	$195.10	$195.10
7 purchase totals =	$1,039.25		$1,121.9612	$1,121.95	$1,121.95	$1,122.00