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	$218.72	9.471%	$239.435	$239.44	$239.45	$239.40
Purchase #2	$131.83	4.244%	$137.4249	$137.42	$137.40	$137.40
Purchase #3	$52.88	3.653%	$54.8117	$54.81	$54.80	$54.80
Purchase #4	$39.58	8.284%	$42.8588	$42.86	$42.85	$42.90
Purchase #5	$166.70	13.275%	$188.8294	$188.83	$188.85	$188.80
Purchase #6	$245.31	6.208%	$260.5388	$260.54	$260.55	$260.50
Purchase #7	$84.87	13.111%	$95.9973	$96.00	$96.00	$96.00
7 purchase totals =	$939.89		$1,019.8959	$1,019.90	$1,019.90	$1,019.80