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	$247.55	7.116%	$265.1657	$265.17	$265.15	$265.20
Purchase #2	$98.57	13.405%	$111.7833	$111.78	$111.80	$111.80
Purchase #3	$64.58	12.314%	$72.5324	$72.53	$72.55	$72.50
Purchase #4	$189.57	5.684%	$200.3452	$200.35	$200.35	$200.30
Purchase #5	$39.96	5.379%	$42.1094	$42.11	$42.10	$42.10
Purchase #6	$245.90	5.542%	$259.5278	$259.53	$259.55	$259.50
Purchase #7	$137.48	5.363%	$144.8531	$144.85	$144.85	$144.90
7 purchase totals =	$1,023.61		$1,096.3169	$1,096.32	$1,096.35	$1,096.30