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	$241.47	7.198%	$258.851	$258.85	$258.85	$258.90
Purchase #2	$38.83	6.674%	$41.4215	$41.42	$41.40	$41.40
Purchase #3	$72.57	10.404%	$80.1202	$80.12	$80.10	$80.10
Purchase #4	$216.87	6.832%	$231.6866	$231.69	$231.70	$231.70
Purchase #5	$82.59	12.204%	$92.6693	$92.67	$92.65	$92.70
Purchase #6	$84.25	7.276%	$90.38	$90.38	$90.40	$90.40
Purchase #7	$160.86	9.715%	$176.4875	$176.49	$176.50	$176.50
7 purchase totals =	$897.44		$971.6161	$971.62	$971.60	$971.70