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	$88.70	9.663%	$97.2711	$97.27	$97.25	$97.30
Purchase #2	$60.33	3.775%	$62.6075	$62.61	$62.60	$62.60
Purchase #3	$201.72	3.577%	$208.9355	$208.94	$208.95	$208.90
Purchase #4	$97.75	6.835%	$104.4312	$104.43	$104.45	$104.40
Purchase #5	$19.82	5.404%	$20.8911	$20.89	$20.90	$20.90
Purchase #6	$8.33	6.688%	$8.8871	$8.89	$8.90	$8.90
Purchase #7	$87.66	12.664%	$98.7613	$98.76	$98.75	$98.80
7 purchase totals =	$564.31		$601.7848	$601.79	$601.80	$601.80