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	$186.34	7.720%	$200.7254	$200.73	$200.75	$200.70
Purchase #2	$110.42	9.446%	$120.8503	$120.85	$120.85	$120.90
Purchase #3	$10.72	4.479%	$11.2001	$11.20	$11.20	$11.20
Purchase #4	$72.60	10.544%	$80.2549	$80.25	$80.25	$80.30
Purchase #5	$239.39	8.435%	$259.5825	$259.58	$259.60	$259.60
Purchase #6	$168.40	11.293%	$187.4174	$187.42	$187.40	$187.40
Purchase #7	$228.72	4.198%	$238.3217	$238.32	$238.30	$238.30
7 purchase totals =	$1,016.59		$1,098.3523	$1,098.35	$1,098.35	$1,098.40