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	$250.90	7.548%	$269.8379	$269.84	$269.85	$269.80
Purchase #2	$90.32	11.156%	$100.3961	$100.40	$100.40	$100.40
Purchase #3	$39.26	7.766%	$42.3089	$42.31	$42.30	$42.30
Purchase #4	$53.94	4.736%	$56.4946	$56.49	$56.50	$56.50
Purchase #5	$235.59	5.606%	$248.7972	$248.80	$248.80	$248.80
Purchase #6	$112.48	6.512%	$119.8047	$119.80	$119.80	$119.80
Purchase #7	$210.88	12.715%	$237.6934	$237.69	$237.70	$237.70
7 purchase totals =	$993.37		$1,075.3328	$1,075.33	$1,075.35	$1,075.30