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	$99.32	5.813%	$105.0935	$105.09	$105.10	$105.10
Purchase #2	$233.58	3.797%	$242.449	$242.45	$242.45	$242.40
Purchase #3	$43.70	5.453%	$46.083	$46.08	$46.10	$46.10
Purchase #4	$243.66	13.474%	$276.4907	$276.49	$276.50	$276.50
Purchase #5	$80.42	12.202%	$90.2328	$90.23	$90.25	$90.20
Purchase #6	$77.55	3.832%	$80.5217	$80.52	$80.50	$80.50
Purchase #7	$214.91	9.869%	$236.1195	$236.12	$236.10	$236.10
7 purchase totals =	$993.14		$1,076.9902	$1,076.98	$1,077.00	$1,076.90