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	$41.92	3.482%	$43.3797	$43.38	$43.40	$43.40
Purchase #2	$77.55	10.176%	$85.4415	$85.44	$85.45	$85.40
Purchase #3	$106.80	11.846%	$119.4515	$119.45	$119.45	$119.50
Purchase #4	$172.95	3.354%	$178.7507	$178.75	$178.75	$178.80
Purchase #5	$166.58	12.620%	$187.6024	$187.60	$187.60	$187.60
Purchase #6	$79.59	3.545%	$82.4115	$82.41	$82.40	$82.40
Purchase #7	$131.82	12.714%	$148.5796	$148.58	$148.60	$148.60
7 purchase totals =	$777.21		$845.6169	$845.61	$845.65	$845.70