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	$46.92	11.533%	$52.3313	$52.33	$52.35	$52.30
Purchase #2	$248.65	11.107%	$276.2676	$276.27	$276.25	$276.30
Purchase #3	$182.90	12.830%	$206.3661	$206.37	$206.35	$206.40
Purchase #4	$90.27	10.548%	$99.7917	$99.79	$99.80	$99.80
Purchase #5	$21.34	6.584%	$22.745	$22.75	$22.75	$22.70
Purchase #6	$126.52	11.750%	$141.3861	$141.39	$141.40	$141.40
Purchase #7	$37.33	3.411%	$38.6033	$38.60	$38.60	$38.60
7 purchase totals =	$753.93		$837.4911	$837.50	$837.50	$837.50