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	$196.91	12.507%	$221.5375	$221.54	$221.55	$221.50
Purchase #2	$166.33	7.345%	$178.5469	$178.55	$178.55	$178.50
Purchase #3	$214.54	12.448%	$241.2459	$241.25	$241.25	$241.20
Purchase #4	$123.70	5.824%	$130.9043	$130.90	$130.90	$130.90
Purchase #5	$169.54	7.546%	$182.3335	$182.33	$182.35	$182.30
Purchase #6	$132.77	9.212%	$145.0008	$145.00	$145.00	$145.00
Purchase #7	$136.88	3.614%	$141.8268	$141.83	$141.85	$141.80
7 purchase totals =	$1,140.67		$1,241.3957	$1,241.40	$1,241.45	$1,241.20