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	$172.89	3.554%	$179.0345	$179.03	$179.05	$179.00
Purchase #2	$184.33	6.364%	$196.0608	$196.06	$196.05	$196.10
Purchase #3	$229.79	4.639%	$240.45	$240.45	$240.45	$240.50
Purchase #4	$183.29	13.685%	$208.3732	$208.37	$208.35	$208.40
Purchase #5	$63.90	10.158%	$70.391	$70.39	$70.40	$70.40
Purchase #6	$217.33	6.506%	$231.4695	$231.47	$231.45	$231.50
Purchase #7	$40.54	8.457%	$43.9685	$43.97	$43.95	$44.00
7 purchase totals =	$1,092.07		$1,169.7475	$1,169.74	$1,169.70	$1,169.90