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	$131.45	8.448%	$142.5549	$142.55	$142.55	$142.60
Purchase #2	$38.86	12.801%	$43.8345	$43.83	$43.85	$43.80
Purchase #3	$43.28	11.359%	$48.1962	$48.20	$48.20	$48.20
Purchase #4	$180.80	3.473%	$187.0792	$187.08	$187.10	$187.10
Purchase #5	$42.34	10.310%	$46.7053	$46.71	$46.70	$46.70
Purchase #6	$68.96	13.783%	$78.4648	$78.46	$78.45	$78.50
Purchase #7	$193.72	3.385%	$200.2774	$200.28	$200.30	$200.30
7 purchase totals =	$699.41		$747.1123	$747.11	$747.15	$747.20