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	$142.53	5.659%	$150.5958	$150.60	$150.60	$150.60
Purchase #2	$222.77	9.498%	$243.9287	$243.93	$243.95	$243.90
Purchase #3	$200.84	8.429%	$217.7688	$217.77	$217.75	$217.80
Purchase #4	$41.70	7.492%	$44.8242	$44.82	$44.80	$44.80
Purchase #5	$213.34	4.363%	$222.648	$222.65	$222.65	$222.60
Purchase #6	$120.40	5.827%	$127.4157	$127.42	$127.40	$127.40
Purchase #7	$51.83	7.118%	$55.5193	$55.52	$55.50	$55.50
7 purchase totals =	$993.41		$1,062.7005	$1,062.71	$1,062.65	$1,062.60