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	$102.88	10.533%	$113.7164	$113.72	$113.70	$113.70
Purchase #2	$200.51	13.316%	$227.2099	$227.21	$227.20	$227.20
Purchase #3	$221.38	13.459%	$251.1755	$251.18	$251.20	$251.20
Purchase #4	$148.71	10.858%	$164.8569	$164.86	$164.85	$164.90
Purchase #5	$55.30	7.269%	$59.3198	$59.32	$59.30	$59.30
Purchase #6	$179.61	9.589%	$196.8328	$196.83	$196.85	$196.80
Purchase #7	$204.92	13.668%	$232.9285	$232.93	$232.95	$232.90
7 purchase totals =	$1,113.31		$1,246.0398	$1,246.05	$1,246.05	$1,246.00