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	$148.75	6.133%	$157.8728	$157.87	$157.85	$157.90
Purchase #2	$85.53	5.812%	$90.501	$90.50	$90.50	$90.50
Purchase #3	$46.83	6.709%	$49.9718	$49.97	$49.95	$50.00
Purchase #4	$76.46	3.843%	$79.3984	$79.40	$79.40	$79.40
Purchase #5	$203.45	13.780%	$231.4854	$231.49	$231.50	$231.50
Purchase #6	$174.74	6.362%	$185.857	$185.86	$185.85	$185.90
Purchase #7	$169.41	10.256%	$186.7847	$186.78	$186.80	$186.80
7 purchase totals =	$905.17		$981.8711	$981.87	$981.85	$982.00