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	$142.72	5.502%	$150.5725	$150.57	$150.55	$150.60
Purchase #2	$53.46	11.186%	$59.44	$59.44	$59.45	$59.40
Purchase #3	$169.25	13.242%	$191.6621	$191.66	$191.65	$191.70
Purchase #4	$246.59	13.384%	$279.5936	$279.59	$279.60	$279.60
Purchase #5	$139.80	12.128%	$156.7549	$156.75	$156.75	$156.80
Purchase #6	$138.47	3.138%	$142.8152	$142.82	$142.80	$142.80
Purchase #7	$85.44	3.801%	$88.6876	$88.69	$88.70	$88.70
7 purchase totals =	$975.73		$1,069.5259	$1,069.52	$1,069.50	$1,069.60